Performance notes of Garmin drawing routines

All tests ran in simulator with FR955, and low power mode with Watch face diagnostics.

Notably Profiler is useless, it won't give even remotely same numbers. Only the watch face diagnostics screen gives accurate numbers when it comes to onPowerBudgetExceeded limitations.

Tested with IQ 4.1.4 SDK.

1. Drawing full bitmap from BufferedBitmapReference:

Ex01FullBitmapDraw, simply draw whole bitmap on each update:

dc.drawBitmap(0, 0, buffer);

Total time: 55123
Execution time: 862
Graphics time: 181
Display time: 54080

2. Drawing half of bitmap BufferedBitmapReference with setClip

Example view: Ex02HalfBitmapDrawClip in low power mode:

dc.setClip(0, 0, dc.getWidth(), dc.getHeight() / 2);
dc.drawBitmap(0, 0, buffer);

Total time: 28202
Execution time: 1062
Graphics time: 100
Display time: 27040

2. (B) Drawing right half of bitmap BufferedBitmapReference with setClip

Example view: Ex02HalfBitmapDrawClip02, this is where it gets confusing. Drawing right half takes as long as drawing whole screen!

dc.setClip(dc.getWidth() / 2, 0, dc.getWidth() / 2, dc.getHeight());
dc.drawBitmap(0, 0, buffer);

Total time: 55398
Execution time: 1137
Graphics time: 181
Display time: 54080

3. Drawing half of bitmap BufferedBitmapReference with drawOffsetBitmap

Ex03HalfBitmapDrawOffset notably, this renders exactly same screen as 2. but is very slow! First finding! Never use drawOffsetBitmap, instead use setClip like in previous.

dc.drawOffsetBitmap(0, 0, 0, 0, dc.getWidth(), dc.getHeight() / 2, buffer);

Total time: 55285
Execution time: 1024
Graphics time: 181
Display time: 54080

4. Drawin quarter of full bitmap with setClip

Ex04QuarterBitmap another finding! This takes longer than drawing half a screen of bitmap? What is going on?

dc.setClip(dc.getWidth() / 2, 0, dc.getWidth() / 2, dc.getHeight() / 2);
dc.drawBitmap(0, 0, buffer);

Total time: 28289
Execution time: 1149
Graphics time: 100
Display time: 27040

5. Drawing quarter of quarter bitmap with drawBitmap's offset

Ex05QuarterBitmapOffset another finding! This takes longer than drawing quarter of a screen of bitmap, this time drawBitmap first and second argument are not helping!

// onLayout
var buffer = Graphics.createBufferedBitmap({
    :width => dc.getWidth() / 2,
    :height => dc.getHeight() / 2,
})

// onPartialUpdate:
dc.drawBitmap(dc.getWidth() / 2, 0, buffer);

Total time: 55198
Execution time: 938
Graphics time: 181
Display time: 54080

6. Drawing quarter of quarter bitmap with drawBitmap's offset and dc setClip

Ex06QuaterBitmapClip here we seem to prove that cutting your bitmaps to smaller pieces does not in fact give performance benefits. So far most convinient way to draw a quarter is 4. with just simple setClip.

// onLayout
var buffer = Graphics.createBufferedBitmap({
    :width => dc.getWidth() / 2,
    :height => dc.getHeight() / 2,
})

// onPartialUpdate
dc.setClip(dc.getWidth() / 2, 0, dc.getWidth() / 2, dc.getHeight() / 2);
dc.drawBitmap(dc.getWidth() / 2, 0, buffer);

Total time: 28364
Execution time: 1224
Graphics time: 100
Display time: 27040

7. Drawing small rectangles (smaller than quarter of screen) from full bitmap with setClip

Ex07SmallClips another finding, re-drawing a same buffer with different clips is total waste. This is slower than drawing half of the screen!

dc.setClip(0, 0, 50, 50);
dc.drawBitmap(0, 0, buffer);
dc.setClip(50, 50, 50, 50);
dc.drawBitmap(0, 0, buffer);
dc.setClip(100, 100, 50, 50);
dc.drawBitmap(0, 0, buffer);

Total time: 33974
Execution time: 2624
Graphics time: 150
Display time: 31200