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Improve performance of screen_get_dpi() in Javascript

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Replace a bisect with a single multiplication when calling
screen_get_dpi() in Javascript

Tested the value of
window.matchMedia(`(resolution:${(window.devicePixelRatio*96).toFixed(100)}dpi)`).matches
which is true except for values that cause a lot of rounding errors
(e.g. dpr : 0.3  => resolution: 28.799999999999997dpi)

Even in these cases the value matches the result of the previous
`findDPI()` method.

See also:

6cff589b5b (r81273660)
(cherry picked from commit c2e3971013)
This commit is contained in:
Jamie Pate 2022-08-15 21:12:19 -07:00 committed by Rémi Verschelde
parent c8810395a2
commit 562d7c616d
1 changed files with 7 additions and 21 deletions
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28
platform/javascript/js/libs/library_godot_display.js
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@ -335,26 +335,12 @@ const GodotDisplay = {
$GodotDisplay__deps: ['$GodotConfig', '$GodotRuntime', '$GodotDisplayCursor', '$GodotEventListeners', '$GodotDisplayScreen', '$GodotDisplayVK'],
$GodotDisplay: {
window_icon: '',
findDPI: function () {
function testDPI(dpi) {
return window.matchMedia(`(max-resolution: ${dpi}dpi)`).matches;
}
function bisect(low, high, func) {
const mid = parseInt(((high - low) / 2) + low, 10);
if (high - low <= 1) {
return func(high) ? high : low;
}
if (func(mid)) {
return bisect(low, mid, func);
}
return bisect(mid, high, func);
}
try {
const dpi = bisect(0, 800, testDPI);
return dpi >= 96 ? dpi : 96;
} catch (e) {
return 96;
}
getDPI: function () {
// devicePixelRatio is given in dppx
// https://drafts.csswg.org/css-values/#resolution
// > due to the 1:96 fixed ratio of CSS *in* to CSS *px*, 1dppx is equivalent to 96dpi.
const dpi = Math.round(window.devicePixelRatio * 96);
return dpi >= 96 ? dpi : 96;
},
},
@ -472,7 +458,7 @@ const GodotDisplay = {
godot_js_display_screen_dpi_get__sig: 'i',
godot_js_display_screen_dpi_get: function () {
return GodotDisplay.findDPI();
return GodotDisplay.getDPI();
},
godot_js_display_pixel_ratio_get__sig: 'f',