I have a UIView subclass with the drawRect: method overriden. In there, I have long lines of generated code that draw something.
The generated code has a problem of having all the vertices/coordinates of the paths/lines hard-coded. So, to draw a 100x100 square, it would start at 0,0 and go to 0,100 -> 100,100 -> 100,0. To make this shape scale based on the UIView bounds property was done as follows:
// This is the size of the drawing. I always know this value beforehand.
CGSize contentSize = SHAPE_XMARK_SIZE;
CGFloat scaleX = self.bounds.size.width / contentSize.width;
CGFloat scaleY = self.bounds.size.height / contentSize.height;
CGContextScaleCTM(context, MIN(scaleX, scaleY), MIN(scaleX, scaleY));
All good as far as the scale is concerned. Now, I would like the position of the drawing to be ralative to the bounds, too. I want to somehow make the drawRect: method align the drawing based on the bounds, too.
I am thinking of something like:
push context method
draw code
pop context
position previous context
Is that a sane approach? Or is the push and pop context not able to accomplish such sorcery?
One Simple Approach:
To answer the "what have you tried" question, I tried making the view that I draw isolated with a bounds size equal to the drawing size, then embed that view inside another view... and it works. However, this method is tedious and I would prefer avoiding it, if possible.
Pfft, the answer was super simple. Me 1, SO 0, I guess.
CGContextTranslateCTM(context, xOffset, yOffset);
Yeah, I somehow overlooked the fact that an awesome function should exist to translate CGContextRef, since the scale function existed.
The rest is all simple math to achieve vertical & horizontal alignment.
Related
Is it possible to specify an initial offset of the image when using drawAsPatternInRect of the UIImage class?
To clarify what I actually need:
Let's say I'm drawing an image in the center of a view, using the drawAsPatternInRect. Now if I move this rectangular area around, the drawn background still fills the whole area, but it's coordinates are fixed, i.e. they do not move with the rect, which makes it look like the drawing area is just a transparent 'window' to some static background. What I would like to achieve is to make it look like the background is moving together with the area itself.
I've tried using the functions described here, but I didn't have much success.
Any help would be very welcome.
CGFloat hOffset = ...
CGFloat vOffset = ...
CGContextSetPatternPhase(context, CGSizeMake(hOffset, vOffset));
Invoke it just before invoking drawAsPatternInRect
The question has changed, please read the entire post.
I must be missing something. I've successfully done this with rotations around the y axis but when I try to do it around the x axis everything gets messed up and I'm not sure why. The idea is to rotate the layer around an edge (in this case, the bottom edge). The view will rotate into and out of visibility. I've searched Stack Exchange, Googled it, read a couple tutorials and read the Apple doc's. My head is telling me this should work but it's just not. I get the kind of animation I want, but it's rotating around the top edge. I can get it to rotate around the bottom edge but then it's in the wrong direction. Here's my code when it rotates in the correct direction, but around the top edge.
Note I have the anchor set:
rLayer.anchorPoint = CGPointMake(.5f, 0.0f);
Also, the origin of the y is negative size.height when I want the view to disappear. So the percentRotation will be 1, giving me a rotation of M_PI_2. When the origin is 0, the percentRotation is also 0, giving me a rotation of 0. This also allows me to track a drag, which is convenient.
The following code is in a animation block (usually, unless I'm tracking a drag). Note the cRect is the rect I've set the _toolbar.frame to.
CALayer *rLayer = _toolbar.layer;
CGFloat zDist = self.view.window.bounds.size.height * 1.5;
CATransform3D rT = CATransform3DIdentity;
CGFloat percentRotation = 1.0f - ((cRect.size.height + cRect.origin.y) / cRect.size.height);
rT.m34 = 1.0f / -zDist;
rT = CATransform3DRotate(rT, M_PI_2 * percentRotation, 1.0f, 0.0f, 0.0f);
rLayer.transform = rT;
I've also tried using a -M_PI_2, but the view just disappears without animation. Any help would be greatly appreciated.
UPDATE
Ok, I did figure it out, but I'm going to change my question slightly. First, I created a separate project so no other code would interfere with the animations. I learned that to rotate around the bottom x-axis in iOS, the anchor point need to be {0.5f, 1.0f}. Annoying that their docs don't mention that, and with Core-anything, it can be tough to know what the coordinate system is on iOS.
It appears that my code was perfectly fine (aside from the anchor), as it was exactly the same as in the stand alone project. So I started removing other elements off the page. Turns out, I was hiding another view behind the one I was trying to animate. It was also animating (no 3D rotation, though, just position). During the animation, this view was appearing above the view I was trying to rotate. At the end, the rotating view would just appear above the other one, giving the impression that there was no rotation animation.
The 'easy' fix is to forego animating the hidden view. But this makes my code a little more complicated when I want to actually show that view. What I would really like to know is why core-animation is doing this, and what I can do to fix it.
I can't find an answer for this one.
I would like to know how to have the image size in a calayer's to be lower than calayer's bound's size.
I've got several pawns in an iPad game, each is a CALayer and I have them resize simply with a contentsGravity=kCAGravityResizeAspect. Image is 128x128 inside of a CALayer of 30x30 so the image gets resized automatically to 30x30 and because of both being a box, aspect ratio maintains and works.
Here I set CALayer's bounds proportional relative to superview's size, so the Pawns always present the same relative size to the view. This one is inside my sprite class subclass of calayer:
-(void) setSpriteScaleToDice {
CGFloat newSize = [self superlayer].bounds.size.width * 0.066666667f;
self.bounds=CGRectMake(0.0f, 0.0f, newSize, newSize);
self.contentsGravity = kCAGravityResizeAspect;
}
Note that in my case the CALayer bounds gets a maximum of 30x30 which is small for a touch. That's the problem I'm facing, due to this small size it's difficult to "touch" them, sometimes touch fails...
One of the ideas that I'm thinking is to increase the "bounds" of the calayer, while keeping the image at its original size. The problem is that I've search a lot and tried several options with contentsGravity, contentsCenter, contentsScale, etc... without success.
In particular, as per apple docs looks like the way to go is with contentsCenter (and not using contentsGravity), however I get deformation in the bitmap...
Please, any idea is really welcome, and thanks in advance,
Luis
This is probably a silly question, but why are you using CALayers for this instead of UIViews? UIImageView has a contentMode property that lets you do this easily (not to mention being easier to use for touch event handling).
That said, CALayer has a contentsRect property that appears to let you define a sub-rectangle for contents to be drawn within, so that may let you do what you want.
Another option would be to place your image layer inside a larger layer and use that for the hit test.
CAlayer CGFloat contentsScale
/* Defines the scale factor applied to the contents of the layer. If
* the physical size of the contents is '(w, h)' then the logical size
* (i.e. for contentsGravity calculations) is defined as '(w /
* contentsScale, h / contentsScale)'. Applies to both images provided
* explicitly and content provided via -drawInContext: (i.e. if
* contentsScale is two -drawInContext: will draw into a buffer twice
* as large as the layer bounds). Defaults to one. Animatable. */
If you want your image drawn in the CALayer at a size other than the CALayer you need to create your own drawInContext: method and draw the image rather than setting the CALayer's contents property. Do not set the contents property, create your own to track the image you want to draw.
I have a problem understanding how the parameter passed to the drawInRect method is defined when a rotation transformation is performed on a UIView.
To give an example I have a UIView which I rotated with an angle of 307 degree.
In the drawInRect method I log the following:
self.frame: {{103.932, 273.254}, {64.3007, 84.3374}}
rect (the variable passed as parameter:{{0, 0.102913}, {18, 89}}
The problem is that according to the documentation I should not draw outside of rect, but considering what I should draw, there is no way my images will fit there.
Can anyone explain to me how I am supposed to use drawInRect in the case my UIView is rotated ?
To give more detail about my problem, here is what I do:
I have a scrollview with a contentView inside (subclassed). I add my UIViews in the content view.
The views in question are composed of a handler image (bottom left) and the main image (top right). Users are supposed to grab the view by pressing the handler but that's not the point.
The drawInRect method of the UIView contains the following:
[_image drawInRect:CGRectMake(handlerSize.width, 0, _image.size.width, _image.size.height)];
CGSize size = CGSizeMake(kHandPickerWidth/self.scrollViewScale, kHandPickerHeight/self.scrollViewScale);
[_handPickerImage drawInRect:(0, _image.size.height, size.width, size.height)];
The UIViews objects are added at viewWillAppear in the content view doing the following:
first instanciate,
then addSubview:
then I set the scrollViewScale parameter,
then I set the frame parameter (according to the top right image displayed (which may vary)
then I rotate the UIView.
Starting from line three, the code is executed from the
- (void)scrollViewDidZoom:(UIScrollView *)scrollView
to make sure every variable is set properly when displayed is needed.
The line defining the size variable is to adjust the marker's size no mater the zoomScale value of the scroll view.
You basically just draw as you would normally, and the painting will be rotated by iOS for you. You can get this transformation information if you would want to.
You need to get a reference to the currect graphics context:
CGContextRef ctx = UIGraphicsGetCurrentContext();
Then query the transformation matrix directly:
CGAffineTransform tf = CGContextGetCTM(ctx);
NSLog(#"current ctm: %#",NSStringFromCGAffineTransform(tf));
or better, get the transfrom from your drawing function to the device:
CGAffineTransform tf = CGContextGetUserSpaceToDeviceSpaceTransform(ctx);
NSLog(#"user->device transform: %#",NSStringFromCGAffineTransform(tf));
And in drawRect: you should not rely too much on the passed CGRect, because it serves mostly as a hint to what piece of the view needs updating. (e.g. because you called -setNeedsDisplayInRect: on it). To get the actual bounds where your view lives in, use self.bounds.
Drawing outside of the CGRect is no real problem, but will only hurt performance a little.
edit
ps. to clarify: self.frame is the frame of your view in the parent view coordinate system. It changes if you move, rotate or otherwise transform the view. self.bounds is the frame of your view in its own coordinate system, and (therefore) remains constant under changes of position or transformations.
So I found a solution to my problem:
I was setting the frame parameter multiple times with some CGAffineTransformation defined which is not supposed to be done.
Now each time I need to reset the frame I reset the affine transform, change the frame and set the back the affine transform.
Everything works as supposed to this way.
Cocoa's NSScrollView is horribly under-explained. I hope someone here knows what it's all about and can spare me a few seconds.
So I have a custom NSView. I implement -drawRect: for it to draw something, fill itself with colour, whatever. Then I have an NSScrollView wrapping it (set up through the interface Builder).
Now the inner, custom, view must have a size larger than that which fits in the outer scroll view—for it to scroll. That much I realise. I have incidentally configured it so that the scroll view adjusts to the surrounding window’s size, but that shouldn’t matter.
I override my inner view’s -frame method to return a frame sized at least 1000x1000.
- (NSRect)frame {
CGFloat w = 1000;
CGFloat h = 1000;
if (self.superview.bounds.size.width > w)
w = self.superview.bounds.size.width;
if (self.superview.bounds.size.height > h)
h = self.superview.bounds.size.height;
return NSMakeRect(0, 0, w, h);
}
Here’s the outcome, which I have trouble interpreting:
I can scroll when the scroll view encloses an area smaller than 1000x1000
BUT
The only area filled with colour (i.e. that my -drawRect: method has any effect on) is
as large as the scroll view’s bounds
located at (0,0. I use flipped, so that’s top left, and it ends up being outside the visible area after scrolling.
The visible area that lies outside this irrelevant rectangle is not painted at all.
I don’t know anything beyond this point. It seems like the rect for drawing is clipped to the scroll view’s position in the window, and size, or something—but it does not take the scrolled "location" into account.
It should be noted that I don't really expect anything else to happen. I feel I am missing a piece, but can't find which. Sorry for the wall of text, but I can’t explain better right now. I hope it is easier to answer than it is to ask.
Regards and hope,
Not Rick Astley
It's a very very very bad idea to overwrite -frame. There is so much that depends on the actual instance variable having a correct value. Instead try to set the frame to the one you want using setFrame:, that might fix all your problems if you're lucky...
I agree with Max's warning that you shouldn't override -frame. If you want to constrain the set frame, override its setter ( -setFrame: ) and the designated initializer ( -initWithFrame: ) and adjust the proposed frame as desired.
Regarding your overall problem, I wonder if your problem is conceptual. The argument for -drawRect: (the dirty rectangle you're asked to redraw) is useful if you're drawing something that you can redraw incrementally in parts (like a grid - any grid blocks intersecting dirtyRect can be redrawn and the rest can be ignored). If you're doing something that has to be completely redrawn, you should use [self bounds] and not the dirty rect passed at drawRect.
For example, if you have just a standard gradient background, it's difficult to tell from dirtyRect which part of the gradient to redraw and infinitely easier just to redraw the whole view with the gradient, ignoring dirtyRect altogether.
You're right in assuming that only the area of your view exposed by the scroll view's clip rect will normally be asked to redraw when scrolling. There're also interactions with the scroll view's -copiesOnScroll to consider.
I hope this helps.
Use of the NSScroller really relies on a solid understanding of the MVC paradigm. Apple's docs really focus on showing a photo and a set of text, but not much else. The use of NSScrollView is something that I've struggled with in the past.
First off, do not override frame. Use setFrame to tell the scrollView how large the working area is, and then just simply draw in the area the frame encompasses. As I understand it, a custom NSView and the encompassing NSScrollView takes care of the rest, such as what to draw where when. In other words, ignore the bounds of the rect passed into drawRect and instead draw within the bounds of the frame you sent to scrollView; don't worry about what is visible and what isn't because that is the job of the framework.
Here is where the MVC paradigm comes in: setFrame should be used when your Model is updated. So, if an object falls outside of the current bounds of the frame, then use setFrame to set the newly expanded bounds, and then draw within that area.