Canvas.drawText() doesn't render large emojis on Android

I've come up with a test (an empirical estimation) for the maximum font size at which emojis can still be rendered.

The way this function works is it creates a 1x1 bitmap, and tries to draw the Earth Globe emoji (🌍) in the center of that. Then it checks that single pixel, whether it's still transparent, or colored.

I've chosen the Earth Globe emoji because I assume we can be fairly certain that no artist would ever draw the Earth with a hole in the middle. (Or we're in huge trouble anyway.)

The tests are done in a binary search - fashion, so the runtime should be logarithmic.

(Fun fact: the max font size on both my test phones turned out to be 256.)

public static float getMaxEmojiFontSize() {    return getMaxEmojiFontSize(new Paint(), 8, 999999, 1);}/** * Emojis cannot be renderered above a certain font size due to a bug. * This function tries to estimate what the maximum font size is where emojis can still * be rendered. * @param   p           A Paint object to do the testing with. *                      A simple `new Paint()` should do. * @param   minTestSize From what size should we test if the emojis can be rendered. *                      We're assuming that at this size, emojis can be rendered. *                      A good value for this is 8. * @param   maxTestSize Until what size should we test if the emojis can be rendered. *                      This can be the max font size you're planning to use. * @param   maxError    How close should we be to the actual number with our estimation. *                      For example, if this is 10, and the result from this function is *                      240, then the maximum font size that still renders is guaranteed *                      to be under 250. (If maxTestSize is above 250.) */public static float getMaxEmojiFontSize(Paint p, float minTestSize, float maxTestSize, float maxError) {    Bitmap b = Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888);    float sizeLowerLimit = minTestSize; // Start testing from this size    float sizeUpperLimit = maxTestSize;    Canvas c = new Canvas(b);    float size;    for (size = sizeLowerLimit; size < maxTestSize; size *= 2) {        if (!canRenderEmoji(b, c, p, size)) {            sizeUpperLimit = size;            break;        }        sizeLowerLimit = size;    }    // We now have a lower and upper limit for the maximum emoji size.    // Let's proceed with a binary search.    while (sizeUpperLimit - sizeLowerLimit > maxError) {        float middleSize = (sizeUpperLimit + sizeLowerLimit) / 2f;        if (!canRenderEmoji(b, c, p, middleSize)) {            sizeUpperLimit = middleSize;        } else {            sizeLowerLimit = middleSize;        }    }    return sizeLowerLimit;}private static boolean canRenderEmoji(Bitmap b, Canvas can, Paint p, float size) {    final String EMOJI = "\uD83C\uDF0D"; // the Earth Globe (Europe, Africa) emoji - should never be transparent in the center.    can.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR); // clear the canvas with transparent    p.setTextSize(size);    { // draw the emoji in the center        float ascent = Math.abs(p.ascent());        float descent = Math.abs(p.descent());        float halfHeight = (ascent + descent) / 2.0f;        p.setTextAlign(Paint.Align.CENTER);        can.drawText(EMOJI, 0.5f, 0.5f + halfHeight - descent, p);    }    return b.getPixel(0, 0) != 0;}