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• Optimizing drawing on UITableViewCell

  - by Brian

  I am drawing content to a UITableViewCell and it is working well, but I'm trying to understand if there is a better way of doing this. Each cell has the following components: Thumbnail on the left side - could come from server so it is loaded async Title String - variable length so each cell could be different height Timestamp String Gradient background - the gradient goes from the top of the cell to the bottom and is semi-transparent so that background colors shine through with a gloss It currently works well. The drawing occurs as follows: UITableViewController inits/reuses a cell, sets needed data, and calls [cell setNeedsDisplay] The cell has a CALayer for the thumbnail - thumbnailLayer In the cell's drawRect it draws the gradient background and the two strings The cell's drawRect it then calls setIcon - which gets the thumbnail and sets the image as the contents of the thumbnailLayer. If the image is not found locally, it sets a loading image as the contents of the thumbnailLayer and asynchronously gets the thumbnail. Once the thumbnail is received, it is reset by calling setIcon again & resets the thumbnailLayer.contents This all currently works, but using Instruments I see that the thumbnail is compositing with the gradient. I have tried the following to fix this: setting the cell's backgroundView to a view whose drawRect would draw the gradient so that the cell's drawRect could draw the thumbnail and using setNeedsDisplayInRect would allow me to only redraw the thumbnail after it loaded --- but this resulted in the backgroundView's drawing (gradient) covering the cell's drawing (text). I would just draw the thumbnail in the cell's drawRect, but when setNeedsDisplay is called, drawRect will just overlap another image and the loading image may show through. I would clear the rect, but then I would have to redraw the gradient. I would try to draw the gradient in a CAGradientLayer and store a reference to it, so I can quickly redraw it, but I figured I'd have to redraw the gradient if the cell's height changes. Any ideas? I'm sure I'm missing something so any help would be great.

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• ContentControl + RenderTargetBitmap + empty image

  - by Kellls

  Im trying to create some chart images without ever displaying those charts on the screen. I'v been at this for quite a while and tried a lot of different things but nothing seems to work. The code works perfectly if I display the chart in a window first, but if I don't display it in a window, the bitmap is just white with a black border (no idea why). I have tried adding the chart to a border before rendering and giving the border a green borderBrush. In the bitmap, I see the green borderBrush then the black border and white background but no chart. I don't know where the black border is coming from as the chart is not contained in a black border. I have tried adding the chart to a window without calling window.Show() and again just the black boarder and white background. However if I call window.Show() the bitmap contains the chart. I have tried using a drawingVisual as explained here, same result. Here is the code (not including adding the element to a border or window): private static BitmapSource CreateElementScreenshot(FrameworkElement element, int dpi) { if (!element.IsMeasureValid) { Size size = new Size(element.Width, element.Height); element.Measure(size); element.Arrange(new Rect(size)); } element.UpdateLayout(); var scale = dpi/96.0; var renderTargetBitmap = new RenderTargetBitmap ( (int)(scale * element.RenderSize.Width),(int)(scale * element.RenderSize.Height),dpi,dpi,PixelFormats.Default ); // this is waiting for dispatcher to perform measure, arrange and render passes element.Dispatcher.Invoke(((Action)(() => renderTargetBitmap.Render(element))), DispatcherPriority.Render); return renderTargetBitmap; } Note: The chart is a ContentControl. Is there anyway I can get the chart to render without displaying it in a window first?

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• Drawing line Continous.

  - by japs

  Hi All, How to draw line continuous in uiview? I have used below code and it works fine but after drawing line straght when i draw another line then first one gets clear if i do not clear that then they join each other. Please suggest some solution. (void)drawRect:(CGRect)rect { CGContextRef context = UIGraphicsGetCurrentContext(); //for( Line *eachLine in lineArray ) // [eachLine drawInContext:context]; CGContextSetLineWidth(context, 2.0); CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor); CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor); if (firstTouch.x != 0.0 && firstTouch.y != 0.0) { CGRect dotRect = CGRectMake(firstTouch.x - 3, firstTouch.y - 3.0, 5.0, 5.0); CGContextAddEllipseInRect(context, dotRect); CGContextDrawPath(context, kCGPathFillStroke); **CGContextMoveToPoint(context, firstTouch.x, firstTouch.y); for (NSString *onePointString in points) { CGPoint nextPoint = CGPointFromString(onePointString); CGContextAddLineToPoint(context, nextPoint.x, nextPoint.y); }** CGContextStrokePath(context); } else { CGContextSetFillColorWithColor(context, self.backgroundColor.CGColor); CGContextAddRect(context, self.bounds); CGContextFillPath(context); } }

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• Custom UIView using CALayers disappears after 180º rotation or navigation controller pop

  - by Steve Madsen

  I have a created a custom UIView subclass that is exhibiting some strange behavior. It is a spinning wheel selector, and for performance reasons it is drawn entirely into two CALayer instances. The bottom layer is the wheel itself, which is rotated using setAffineTransform: according to touches. The top layer is eye candy. drawRect: is fairly simple. If the control hasn't been drawn yet (or it's been invalidated), it calls a method that creates the images and assigns them to the layer contents property. - (void) drawRect:(CGRect)rect { if (imageLayer == nil) { [self drawIntoImageLayer]; } [self updateWheelRotation]; } When the view controller using this view first appears, everything is fine. There are two instances where the view completely disappears, however: If the device is rotated a full 180°. After a view controller is popped off the navigation stack and the view becomes visible again. drawRect: is not called either time. Interestingly enough, it IS called after a 90° orientation change, and that causes the view to re-appear. How can I ensure that a custom view using CALayers is redrawn properly in these situations?

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• Adding a selection box into an ItemsControl?

  - by Jens

  I have a WPF ItemsControl with a Canvas ItemPanel. Drawing from an internal source, it displays lots of automatically generated Rectangles. As of now, it looks like this: <Window // .. NameSpaces > <Window.Resources> <DataTemplate x:Key="binTemplate"> <Rectangle x:Name="Rect" VerticalAlignment="Bottom" Canvas.Left="10" StrokeThickness="0"> // .. Databinding Height, Width, etc </Rectangle> </DataTemplate> </Window.Resources> <DockPanel x:Name="LayoutRoot" LastChildFill="True"> <ItemsControl ItemsSource="{Binding Bins}" ItemTemplate="{StaticResource binTemplate}"> <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <Canvas MouseDown="Canvas_MouseDown" MouseMove="Canvas_MouseMove" MouseUp="Canvas_MouseUp"> <Rectangle x:Name="Selection" Canvas.Left="0" Canvas.Top="0" Visibility="Hidden" /> </Canvas> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> </ItemsControl> </DockPanel> </Window> I now try to implement a selection box, too.. well.. select my Rectangles. =) I tried just adding the box into the ItemsControl PanelTemplate, and controlling it with the Canvas mouse events, but it appears I am not allowed to do so. The error message is "Cannot explicitly modify Children collection of Panel used as ItemsPanel for ItemsControl. ItemsControl generates child elements for Panel." What is the preferred way to implement such behavior? I thought about overlaying another canvas (using negative Margin) and drawing the selection box in there, but that seems like a bad hack. Thanks in advance!

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• Objective-C NSDate memory issue (again)

  - by Toby Wilson

  I'm developing a graphing application and am attempting to change the renderer from OpenGL to Quartz2D to make text rendering easier. A retained NSDate object that was working fine before suddenly seems to be deallocating itself, causing a crash when an NSMutableString attempts to append it's decription (now 'nil'). Build & analyse doesn't report any potential problems. Simplified, the code looks like this: NSDate* aDate -(id)init { aDate = [[NSDate date] retain] return self; } -(void)drawRect(CGRect)rect { NSMutableString* stringy = [[NSMutableString alloc] init]; //aDate is now deallocated and pointing at 0x0? [stringy appendString:[aDate description]]; //Crash } I should stress that the actual code is a lot more complicated than that, with a seperate thread also accessing the date object, however suitable locks are in place and when stepping through the code [aDate release] is not being called anywhere. Using [[NSDate alloc] init] bears the same effect. I should also add that init IS the first function to be called. Can anyone suggest something I may have overlooked, or why the NSDate object is (or appears to be) releasing itself?

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• Presenting an image cropping interface

  - by wkw

  I'm trying to engineer a UI for cropping images in iphone OS and suspect I'm going about things the hard way. My goal is pretty much what the Tapbots duo have done with Pastebot. In that app, they dim the source image but provide a movable and resizable cropping view and the image you're cropping is in a zoomable scrollview; when you resize or move the underlying image, the cropping view adjusts appropriately. I mocked up a composite image which will give a sense of the design I'm after, along with how I presently have my view hierarchy setup, viewable here The approach I've started with is the following: UIImageView with the image to crop is in a scrollview, a plain UIView with black fill and suitable transparency/alpha setting is added in front of the imageview. I then use a custom UIView which is a sibling to the scrollview at a higher level, which implements the drawRect: method and for the most part calls CGImageCreateWithImageInRect to get the portion of the image's bitmap that matches the position of the cropping view and draws that to the CGContext. in the viewcontroller I'm using the UIScrollViewDelegate methods to track scrolling and passing those changes to the custom cropping UIView so it stays in sync with the scroll contentOffset. That much is finally working. But trying to keep in sync as the scrollview zoomScale changes is when I figured I should ask for help. Looking for suggestions or guidance. My initial approach just seems like more work than is required. Could this be done with a masking layer in the ImageView? And if so, how would I setup the tracking for moving and resizing the cropping rect? My experience working with layers is non-nil, but very limited thus far.

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• How to create a semi transparent window in WPF that allows mouse events to pass through

  - by RMK

  I am trying to create an effect similar to the Lights out /lights dim feature in Adobe Lightroom (http://www.youtube.com/watch?v=87hNd3vaENE) except in WPF. What I tried was to create another window over-top of my existing window, make it transparent and put a semi transparent Path geometry on it. But I want mouse events to be able to pass through this semi transparent window (on to windows below). This is a simplified version of what I have: <Window x:Class="LightsOut.MaskWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" AllowsTransparency="True" WindowStyle="None" ShowInTaskbar="False" Topmost="True" Background="Transparent"> <Grid> <Button HorizontalAlignment="Left" Height="20" Width="60">click</Button> <Path IsHitTestVisible="False" Stroke="Black" Fill="Black" Opacity="0.3"> <Path.Data> <RectangleGeometry Rect="0,0,1000,1000 "/> </Path.Data> </Path> </Grid> The window is fully transparent, so on places where the Path doesn't cover, mouse events pass right through. So far so good. The IsHitTestvisible is set to false on the path object. So mouse events will pass through it to other controls on the same form (ie you can click on the Button, because it is on the same form). But mouse events wont pass through the Path object onto windows that are below it. Any ideas? Or better ways to solve this problem? Thanks.

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• How can I mix SVG and HTML into a page?

  - by John Duff

  I've been using the jQuery.svg plugin to do some SVG rendering and it works perfectly but I also want to have the server render some SVG into the page and I can't get that to work. How do I add some SVG like below into the page so that Firefox will render it? <svg xmlns="http://www.w3.org/2000/svg" version="1.1" preserveAspectRatio="none" viewBox="0 0 100 100"> <linearGradient id="background_gradient_black" x1="0%" y1="10" x2="0%" y2="90" gradientUnits="userSpaceOnUse"> <stop offset="0%" stop-color="#000" stop-opacity="1" /> <stop offset="45%" stop-color="#444" stop-opacity="1" /> <stop offset="55%" stop-color="#444" stop-opacity="1" /> <stop offset="100%" stop-color="#000" stop-opacity="1" /> </linearGradient> <rect x="0" y="0" width="100" height="100" fill="url(#background_gradient_black)"" /> </svg> Do I need a meta tag saying that there is SVG content in the page or define the SVG namespace somehow?

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• Extended SurfaceView onDraw never called

  - by Gab Royer

  Hi, I'm trying to modify the SurfaceView I use for doing a camera preview in order to display an overlaying square. However, the onDraw method of the extended SurfaceView is never called. Here is the source : public class CameraPreviewView extends SurfaceView { protected final Paint rectanglePaint = new Paint(); public CameraPreviewView(Context context, AttributeSet attrs) { super(context, attrs); rectanglePaint.setARGB(255, 200, 0, 0); rectanglePaint.setStyle(Paint.Style.FILL); rectanglePaint.setStrokeWidth(2); } @Override protected void onDraw(Canvas canvas){ canvas.drawRect(new Rect(10,10,200,200), rectanglePaint); Log.w(this.getClass().getName(), "On Draw Called"); } } public class CameraPreview extends Activity implements SurfaceHolder.Callback{ private SurfaceHolder holder; private Camera camera; @Override protected void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); // We remove the status bar, title bar and make the application fullscreen requestWindowFeature(Window.FEATURE_NO_TITLE); getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); // We set the content view to be the layout we made setContentView(R.layout.camera_preview); // We register the activity to handle the callbacks of the SurfaceView CameraPreviewView surfaceView = (CameraPreviewView) findViewById(R.id.camera_surface); holder = surfaceView.getHolder(); holder.addCallback(this); holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); } public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { Camera.Parameters params = camera.getParameters(); params.setPreviewSize(width, height); camera.setParameters(params); try { camera.setPreviewDisplay(holder); } catch (IOException e) { e.printStackTrace(); } camera.startPreview(); } public void surfaceCreated(SurfaceHolder holder) { camera = Camera.open(); } public void surfaceDestroyed(SurfaceHolder holder) { camera.stopPreview(); camera.release(); } }

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• Trouble with custom WPF Panel-derived class

  - by chaiguy

  I'm trying to write a custom Panel class for WPF, by overriding MeasureOverride and ArrangeOverride but, while it's mostly working I'm experiencing one strange problem I can't explain. In particular, after I call Arrange on my child items in ArrangeOverride after figuring out what their sizes should be, they aren't sizing to the size I give to them, and appear to be sizing to the size passed to their Measure method inside MeasureOverride. Am I missing something in how this system is supposed to work? My understanding is that calling Measure simply causes the child to evaluate its DesiredSize based on the supplied availableSize, and shouldn't affect its actual final size. Here is my full code (the Panel, btw, is intended to arrange children in the most space-efficient manner, giving less space to rows that don't need it and splitting remaining space up evenly among the rest--it currently only supports vertical orientation but I plan on adding horizontal once I get it working properly): protected override Size MeasureOverride( Size availableSize ) { foreach ( UIElement child in Children ) child.Measure( availableSize ); return availableSize; } protected override System.Windows.Size ArrangeOverride( System.Windows.Size finalSize ) { double extraSpace = 0.0; var sortedChildren = Children.Cast<UIElement>().OrderBy<UIElement, double>( new Func<UIElement, double>( delegate( UIElement child ) { return child.DesiredSize.Height; } ) ); double remainingSpace = finalSize.Height; double normalSpace = 0.0; int remainingChildren = Children.Count; foreach ( UIElement child in sortedChildren ) { normalSpace = remainingSpace / remainingChildren; if ( child.DesiredSize.Height < normalSpace ) // if == there would be no point continuing as there would be no remaining space remainingSpace -= child.DesiredSize.Height; else { remainingSpace = 0; break; } remainingChildren--; } extraSpace = remainingSpace / Children.Count; double offset = 0.0; foreach ( UIElement child in Children ) { //child.Measure( new Size( finalSize.Width, normalSpace ) ); double value = Math.Min( child.DesiredSize.Height, normalSpace ) + extraSpace; child.Arrange( new Rect( 0, offset, finalSize.Width, value ) ); offset += value; } return finalSize; }

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• UISlider won't display

  - by user290295

  I have been having a lot of difficulty adding custom track images to a UISlider. Whenever I do this, whether to a nib created UISlider or a hand programmed UISlider the slider refuses to display. Also, I even commented the track image code out below and the UISlider still refuses to display. There are other nib created sliders in the controlView that display and function fine. if (![self loadView:keyboardControlView intoSuperview:controlView withNib:@"KeyboardControl"]) { NSLog(@"Could not load controlView from nib into synthControlView"); } // nibSlider is an outlet to a UISlider in the above loaded nib file CGRect sliderFrame = nibSlider.frame; float sliderMinimum = nibSlider.minimumValue; float sliderMaximum = nibSlider.maximumValue; float sliderValue = nibSlider.value; // remove from superview, implicitly releasing UISlider [nibSlider removeFromSuperview]; // reuse pointer to allocate new UISlider using rect obtained from nib nibSlider = [[UISlider alloc] initWithFrame:sliderFrame]; nibSlider.backgroundColor = [UIColor clearColor]; nibSlider.minimumValue = sliderMinimum; nibSlider.maximumValue = sliderMaximum; nibSlider.continuous = YES; nibSlider.value = sliderValue; //[nibSlider setMinimumTrackImage:[[UIImage imageNamed:@"violetslider.png"] //stretchableImageWithLeftCapWidth:5.0 topCapHeight:0.0] forState:UIControlStateNormal]; // //[nibSlider setMaximumTrackImage:[[UIImage imageNamed:@"violetslider.png"] // stretchableImageWithLeftCapWidth:5.0 topCapHeight:0.0] forState:UIControlStateNormal]; [nibSlider addTarget:delegate action:@selector(sliderUpdate:) forControlEvents:UIControlEventValueChanged]; [controlView addSubview:nibSlider]; // do not release here as slider will need to remain cached. push onto a release stack. [nibSlider setNeedsDisplay];

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• Can't draw UImage in UIView::drawRect

  - by Joel

  I know this seems like a simple task, which is why I don't understand why I can't get the image to render. When I set up my UIView, I do the following: myUiView.backgroundColor = [UIColor clearColor]; myUiView.opaque = NO; I create and retain the UIImage in the init function of my UIView: image = [[UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"test" ofType:@"png"]] retain]; then my drawRect looks like this: - (void) drawRect:(CGRect) rect { [image drawInRect:self.bounds]; } Ultimately I'll be manipulating that UIImage via bitmap context, and then in drawRect create a CGImage out of the context, and render that, but for now I'm just trying to get it rendering a known image. I've been digging through this site, as well as the documentation. I've gone down the CG path and tried drawing it with CGContextDrawImage by following the numerous examples other people have posted, but that didn't work either. So I've come back to what seems to be the most straightforward way to draw an image, but it isn't working. Any help would be greatly appreciated. Thanks in advance.

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• Using Quartz to draw every second via NSTimer (iPhone)

  - by stuartloxton

  Hi, I'm relatively new to Objective-C + Quartz and am running into what is probably a very simple issue. I have a custom UIView sub class which I am using to draw simple rectangles via Quartz. However I am trying to hook up an NSTimer so that it draws a new object every second, the below code will draw the first rectangle but will never draw again. The function is being called (the NSLog is run) but nothing is draw. Code: - (void)drawRect:(CGRect)rect { context = UIGraphicsGetCurrentContext(); [self step:self]; [NSTimer scheduledTimerWithTimeInterval:(NSTimeInterval)(2) target:self selector:@selector(step:) userInfo:nil repeats:TRUE]; } - (void) step:(id) sender { static double trans = 0.5f; CGContextSetRGBFillColor(context, 1, 0, 0, trans); CGContextAddRect(context, CGRectMake(10, 10, 10, 10)); CGContextFillPath(context); NSLog(@"Trans: %f", trans); trans += 0.01; } context is in my interface file as: CGContextRef context; Any help will be greatly appreciated!

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• Iphone SDK quesiton: How to make a Drawing method in a View class work using CGContextRef?

  - by SimpleCode

  I have these 2 methods in the View class. the drawRect method always gets called when the view is initalized. But i can't get the drawLine method to work. It doesn't do anything when it gets called. Am i supposed to deal with cgimagecontext or something like that? please help!! (void)drawRect:(CGRect)rect { // Drawing code // Drawing code CGContextRef contextRef = UIGraphicsGetCurrentContext(); //CGContextSetRGBFillColor(contextRef, 0, 0, 255, 1); CGContextSetRGBStrokeColor(contextRef, 0, 0, 0, 1); CGContextSetLineWidth(contextRef, 5.0); CGContextBeginPath(contextRef); CGContextMoveToPoint(contextRef, 0, 0); CGContextAddLineToPoint(contextRef, 320, 480); CGContextStrokePath(contextRef); } -(void)drawLine:(CGPoint)from to:(CGPoint) to { // Drawing code CGContextRef contextRef = UIGraphicsGetCurrentContext(); //CGContextSetRGBFillColor(contextRef, 0, 0, 255, 1); CGContextSetRGBStrokeColor(contextRef, 0, 128, 0, 1); CGContextSetLineWidth(contextRef, 5.0); CGContextBeginPath(contextRef); CGContextMoveToPoint(contextRef, 0, 0); CGContextAddLineToPoint(contextRef, 320, 50); CGContextStrokePath(contextRef); }

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• How to move from custom to transluscent NavigationBar and back? Display problems!

  - by jd291

  So, i got this Navigation-based App (with a custom NavigationBar - Category) and I have 2 problems here... @implementation UINavigationBar (Custom) - (void)drawRect:(CGRect)rect { UIImage *image = [UIImage imageNamed: @"bg_toolbar.png"]; [image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)]; } @end Because of the Navigation-based App, most of the views have a height of 436px (= ScreenSize - NavigationBar height, as you probably know ;). I got one view similar to the photo app overview showing all the thumbnails, from there I push a viewcontroller containing the scroll view (like in photos app) on the stack, like so - (void)buttonPressed:(id)sender { UIButton *btn = (UIButton *)sender; PhotoSetScrollViewController *psc = [[PhotoSetScrollViewController alloc] initWithPhotoArray:photos andID:btn.tag]; [self.navigationController pushViewController:psc animated:YES]; } Problem 1: The view holding the fullscreen scrollview has a height of 480px which seems to be a problem because when poping the viewcontroller by hitting the back button, the view containing the thumbnails (height 436px) moves upward below the navigation bar. And also the Toolbar keeps showing. What could be the problem? Problem 2: How could I switch between my custom navigation bar and the standard black translucent style?

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• RectangleGeometry with relative dimensions... how?

  - by Padu Merloti

  I'm trying to replicate the nowadays so fashionable "reflex" effect on a controltemplate for buttons I'm creating. The basic idea is to create a rectangle with a gradient fill from white to transparent and then clip some of that semi-transparent rectangle with a rectanglegeometry. The problem is that I don't know how to define a relative rectangle geometry. I kind of worked around width by defining a large value (1000), but height is a problem. For example, it works good for buttons that have a 200 height, but doesn't do anything for smaller buttons. Any ideas? <Rectangle RadiusX="5" RadiusY="5" StrokeThickness="1" Stroke="Transparent"> <Rectangle.Fill> <LinearGradientBrush StartPoint="0,0" EndPoint="0,0.55"> <GradientStop Color="#66ffffff" Offset="0.0" /> <GradientStop Color="Transparent" Offset="1.0" /> </LinearGradientBrush> </Rectangle.Fill> <Rectangle.Clip> <RectangleGeometry Rect="0,0,1000,60" /> </Rectangle.Clip> </Rectangle>

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• WYSIWYG with Qt - font size woes

  - by Rob

  I am creating a custom Qt widget that mimics an A4 printed page and am having problems getting fonts to render at the correct size. My widget uses QPainter::setViewport and QPainter::setWindow to mimic the A4 page, using units of 10ths of a millimetre which enables me to draw easily. However, attempting to create a font at a specific point size doesn't seem to work and using QFont:setPixelSize isn't accurate. Here is some code: View::View(QWidget *parent) : QWidget(parent), printer(new QPrinter) { printer->setPaperSize(QPrinter::A4); printer->setFullPage(true); } void View::paintEvent(QPaintEvent*) { QPainter painter(this); painter.setWindow(0, 0, 2100, 2970); painter.setViewport(0, 0, printer->width(), printer->height()); // Draw a rect at x = 1cm, y = 1cm, 6cm wide and 1 inch high painter.drawRect(100, 100, 600, 254); // Create a 72pt (1 inch) high font QFont font("Arial"); font.setPixelSize(254); painter.setFont(font); // Draw in the same box // The font is too large painter.drawText(QRect(100, 100, 600, 254), tr("Wg\u0102")); // Ack - the actual font size reported by the metrics is 283 pixels! const QFontMetrics fontMetrics = painter.fontMetrics(); qDebug() << "Font height = " << fontMetrics.height(); } So I'm asking for a 254 high font (1 inch, 72 pts) and it's too big and sure enough when I query for the font height via QFontMetrics it is 283 high. Does anyone else know how to use font sizes in points when using custom mapping modes like this? It must be possible. Note that I cannot see how to convert between logical/device points either (i.e. the Win32 DPtoLP/LPtoDP equivalents.)

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• Two Problems I'm having with UIButton and UIView.

  - by Andy

  Hi all, I haven't been programming on the iPhone for very long, but I'm picking it up slowly by googling problems I get. Unfortunately I haven't been able to find an answer for these. I have started a new View-based application in Xcode 3.2.2 and immediately added the following files: myUIView.m and myUIView.h, which are subclasses of UIView. In Interface Builder, I set the subclass of the default UIView to be myUIView. I made a button in the drawRect method. Problem one: The title of the button only appears AFTER I click the screen, why? Problem two: I want the button to produce the modalview - is this possible? The code is as follow: #import "myUIView.h" @implementation myUIView - (void)drawRect:(CGRect)rect { // Drawing code button = [UIButton buttonWithType:UIButtonTypeRoundedRect]; button.frame = CGRectMake(0,0,100,100); [button setTitle:@"butty" forState:UIControlStateNormal]; [button addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside]; [self addSubview:button]; } -(void)buttonPressed:(id)sender{ NSLog(@"Button pressed"); //present modal view somehow..? } I can't see how to post attachments, but if anyone thinks it will help I can upload the source. Many thanks, Andy

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• CGGradient Not Displaying Correctly on iPad 1 and 2

  - by daveMac

  I have been experimenting with creating my own gradients for the UI in my iOS app. I first used a CAGradientLayer but I was disappointed with the "stepped" look so I have been trying out CGGradient. enter code here I am having an issue with the Gradient displaying correctly. I have three iPads—one for each generation. The gradient looks right on the iPad 3 but not on the iPad 1 or 2. This is really strange. I was going to take a screenshot and post the two differences but even more strange, the screenshot look the same (and yes, the brightness is the same on both). The colors seem really washed out on the older iPads. I know the iPad 3 is a retina display, but I think it must be something more than that. Here is the code I am using: - (void)drawRect:(CGRect)rect { CGContextRef currentContext = UIGraphicsGetCurrentContext(); CGGradientRef skyGradient; CGColorSpaceRef rgbColorspace; size_t num_locations = 3; CGFloat locations[3] = { 0.0, .5, 1.0 }; CGFloat components[12] = { .106, .73, .93333, 1., 0.0, 0.0 , 1.0, 1., .106, .73, .93333, 1. }; rgbColorspace = CGColorSpaceCreateDeviceRGB(); skyGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations); CGRect currentBounds = self.bounds; CGPoint topLeft = CGPointMake(0.0f, 0.0f); CGPoint bottomRight = CGPointMake(CGRectGetMaxX(currentBounds), CGRectGetMaxY(currentBounds)); CGContextDrawLinearGradient(currentContext, skyGradient, topLeft, bottomRight, 0); CGGradientRelease(skyGradient); CGColorSpaceRelease(rgbColorspace); }

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• Can I access views when drawn in the drawRect method?

  - by GianPac

  When creating the content view of a tableViewCell, I used the drawInRect:withFont, drawAtPoint... and others, inside drawRect: since all I needed was to lay some text. Turns out, part of the text drawn need to be clickable URLs. So I decided to create a UIWebView and insert it into my drawRect. Everything seems to be laid out fine, the problem is that interaction with the UIWebView is not happening. I tried enabling the interaction, did not work. I want to know, since with drawRect: I am drawing to the current graphics context, there is anything I can do to have my subviews interact with the user? here is some of my code I use inside the UITableViewCell class. -(void) drawRect:(CGRect)rect{ NSString *comment = @"something"; [comment drawAtPoint:point forWidth:195 withFont:someFont lineBreakMode:UILineBreakModeMiddleTruncation]; NSString *anotherCommentWithURL = @"this comment has a URL http://twtr.us"; UIWebView *webView = [[UIWebView alloc] initWithFrame:someFrame]; webView.delegate = self; webView.text = anotherCommentWithURL; [self addSubView:webView]; [webView release]; } As I said, the view draws fine, but there is no interaction with the webView from the outside. the URL gets embedded into HTML and should be clickable. It is not. I got it working on another view, but on that one I lay the views. Any ideas?

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• C++ Implicit Conversion Operators

  - by Imbue

  I'm trying to find a nice inheritance solution in C++. I have a Rectangle class and a Square class. The Square class can't publicly inherit from Rectangle, because it cannot completely fulfill the rectangle's requirements. For example, a Rectangle can have it's width and height each set separately, and this of course is impossible with a Square. So, my dilemma. Square obviously will share a lot of code with Rectangle; they are quite similar. For examlpe, if I have a function like: bool IsPointInRectangle(const Rectangle& rect); it should work for a square too. In fact, I have a ton of such functions. So in making my Square class, I figured I would use private inheritance with a publicly accessible Rectangle conversion operator. So my square class looks like: class Square : private Rectangle { public: operator const Rectangle&() const; }; However, when I try to pass a Square to the IsPointInRectangle function, my compiler just complains that "Rectangle is an inaccessible base" in that context. I expect it to notice the Rectangle operator and use that instead. Is what I'm trying to do even possible? If this can't work I'm probably going to refactor part of Rectangle into MutableRectangle class. Thanks.

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• iPhone app. Creating a custom UIView that contains UITextField and UIButton.

  - by Dmitry Burchik

  Hi all. I am new to iPhone programming. And I have an issue. I need to create a custom user control that I will add to my UIScrollView dinamically. The control has an UITextField and an UIButton. See the code below: #import <UIKit/UIKit.h> @interface FieldWithValueControl : UIView { UITextField *txtTagName; UIButton *addButton; } @property (nonatomic, readonly) UITextField *txtTagName; @property (nonatomic, readonly) UIButton *addButton; @end #import "FieldWithValueControl.h" #define ITEM_SPACING 10 #define ITEM_HEIGHT 20 #define SWITCHBOX_WIDTH 100 #define SCREEN_WIDTH 320 #define ITEM_FONT_SIZE 14 #define TEXTBOX_WIDTH 150 @implementation FieldWithValueControl @synthesize txtTagName; @synthesize addButton; - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { // Initialization code txtTagName = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, TEXTBOX_WIDTH, ITEM_HEIGHT)]; txtTagName.borderStyle = UITextBorderStyleRoundedRect; addButton = [UIButton buttonWithType:UIButtonTypeContactAdd]; [addButton setFrame:CGRectMake(ITEM_SPACING + TEXTBOX_WIDTH, 0, ITEM_HEIGHT, ITEM_HEIGHT)]; [addButton addTarget:self action:@selector(addButtonTouched:) forControlEvents:UIControlEventTouchUpInside]; [self addSubview:txtTagName]; [self addSubview:addButton]; } return self; } - (void)addButtonTouched:sender { UIButton *button = (UIButton*)sender; NSString *title = [button titleLabel].text; } - (void)drawRect:(CGRect)rect { // Drawing code } - (void)dealloc { [txtTagName release]; [addButton release]; [super dealloc]; } @end In my code I create an object of that class and add it to scrollView on form. FieldWithValueControl *newTagControl = (FieldWithValueControl*)[[FieldWithValueControl alloc] initWithFrame:CGRectMake(ITEM_SPACING, currentOffset + ITEM_SPACING, 0, 0)]; [scrollView addSubview:newTagControl]; The control looks fine, but if I click to the textbox or to the button nothing happens. Keyboard doesn't appear, the button is not clickable etc.

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• drawRect gets called on UIView subclass but not on UIViewController

  - by HotFudgeSunday

  My code is working so far but I had to create a Class for the UIView. This is a bit inconvenient because I need to interact with the ViewController too. BTW, I did try [self setNeedsDisplay] on the ViewDidLoad of the UIViewController subclass file but it didn't work. Here's the code, which works on UIView Subclass but doesn't get called on a UIViewController one: - (void)drawRect:(CGRect)rect { UIColor *currentColor = [UIColor redColor]; CGContextRef context = UIGraphicsGetCurrentContext(); someNum = 1; CGContextBeginPath(context); CGContextMoveToPoint(context, 30, 40); [self addDotImageX:30 andY:40]; CGContextSetLineWidth(context, 2); CGContextSetStrokeColorWithColor(context, currentColor.CGColor); CGContextStrokePath(context); } Any ideas on what to try? BTW, this is a TabBar App. I know those can somehow block the calls to drawRect. The Tabs where created programatically, not through a Nib. Eg: NSMutableArray *listOfViewControllers = [[NSMutableArray alloc] init]; UIViewController *vc; vc = [[Education alloc] init]; vc.title = @"Education"; [listOfViewControllers addObject:vc]; vc.tabBarItem.image = [UIImage imageNamed:@"info.png"]; [vc release]; I would appreciate any ideas. I've been through the answers on this site related to setNeedsDisplay not calling drawRect and haven't found an answer for my particular case. Thanks.

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• Nested functions not allowed in drawrect problem

  - by Martin

  I have a custom view onto which I draw some graphics from the drawrect function, which works fine. However I like to draw based on the contens of an array I pass on the the view just before I do a setNeedsDisplay. In the drawRect function I try to access the array but then I get a nested functions error which I do not understand. Here's my code: // // MyView.h // window // #import <UIKit/UIKit.h> @interface MyView : UIView { NSArray * nary; } @property (nonatomic, copy) NSArray *nary; @end // // MyView.m // window // #import "MyView.h" @implementation MyView @synthesize nary; CGContextRef c; CGFloat black[4] = {0.0f, 0.0f, 0.0f, 1.0f}; - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { // Initialization code } return self; } - (void)drawRect:(CGRect)rect { c = UIGraphicsGetCurrentContext(); CGContextSetStrokeColor(c, black); NSLog(@"mview"); NSArray *ns = [nary objectAtIndex:0]; } - (void)dealloc { [super dealloc]; } @end

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