Pointer pin changes resolution along left/right edge

[Sequynth]

When rotating the view while the pointer pin is at the edge of the screen, the resolution of the pointer pin gradually gets very low, when the pointer pin approaches the center of the left screen edge. Also happens at the center of the right edge of the screen. Does not happen at top or bottom edge

How to Reproduce
Move view away from actual position to get pointer pin; rotate the screen

Versions affected
SC 20.0
Android 6.0

[westnordost]

😆 That is a funny bug. Needless to say, I cannot reproduce it, neither with Android 5 nor Android 7. Haven't tried with an Android 6 though. Which manufacturer?

[matkoniecz]

Reproduced on Xiaomi with Android 6. What would be the first step to debug this?

I see nothing interesting in logs.
Maybe try to display this marker image while horizontal and try whatever static horizontal display is also mangled?

[westnordost]

The code is in PointerPinView. It is a custom view that draws itself in onDraw. Since ony the pin and not the icon itself gets blurred, the relevant code is at line 97-103 :

        val size = min(width, height)
        val r = pinRotation

        pointerPin.setBounds(0,0, size, size)
        c.withRotation(r, width/2f, height/2f) {
            pointerPin.draw(c)
        }

Setting a breakpoint there might help, maybe check if size has a reasonable value. Maybe try if using canvas.width (instead of width) and height solves the problem.

[matkoniecz]

canvas.width: 96 canvas.height: 96 width: 96 height: 96 size: 96 hold constant.

Things get weird with r around 450 and around 630.

Maybe try if using canvas.width (instead of width) and height solves the problem.

Sadly, it has not worked.

EDIT: And I get "Source code does not match the bytecode" on stepping into withRotation

[Sequynth]

Which manufacturer?

LG G4

[westnordost]

Maybe Android 6 doesn't handle angles >= 360° well. Maybe you could try % 360 the rotation.

[westnordost]

If this is in degrees and all and not radians

[westnordost]

Are you still trying it out, @matkoniecz ?

[matkoniecz]

Maybe Android 6 doesn't handle angles >= 360° well. Maybe you could try % 360 the rotation.

Tried that (val r = pinRotation % 360), 270/90 is still problematic.

[matkoniecz]

I unpacked

        c.withRotation(r, width/2f, height/2f) {
            pointerPin.draw(c)
        }

to mostly equivalent form - though one with 90 degree rotation applied everywhere and causing heaviest distortion.

        c.translate(width/2f, height/2f)
        c.rotate(90.0f)
        c.translate(-width/2f, -height/2f)
        pointerPin.draw(c)

the tricky part is that apparently broken rotate is just wrapper around nRotate(mNativeCanvasWrapper, degrees);. And nRotate appears to be a native library function if I am looking at this right.

[matkoniecz]

I tracked it down and confirmed. It is https://stackoverflow.com/questions/36868790/blurry-image-after-canvas-rotate-only-in-android-6 https://issuetracker.google.com/issues/37096313 (found by Android Canvas nRotate Android 6 90 degree search).

Though not an answer, I have managed to find a workaround. This workaround relies on drawing the image onto a canvas, which is linked to a bitmap, which is then drawn onto the final, rotated canvas in the onDraw method.
(...)
with the important part occuring in the onMeasure method:

        if (innerGaugeBitmap != null){
            innerGaugeBitmap.recycle();
        }
        innerGaugeBitmap = Bitmap.createBitmap((int) width, (int) height, Bitmap.Config.ARGB_8888); // Gives LINT-warning draw-allocation, but no other way to upscale bitmaps exists.
        innerGaugeCanvas.setBitmap(innerGaugeBitmap);
        innerGaugeBitmap.eraseColor(Color.TRANSPARENT);
        innerGauge.draw(innerGaugeCanvas);

[westnordost]

Ok, interesting. Will you do a fix, or shall I?

[matkoniecz]

Feel free to fix! I am trying to finally finish one of my open PRs at this moment so I will be perfectly fine to be just a tester for this one.