[HTML5] Detect screen scale and DPI.

`OS.get_screen_scale` will now return the `window.devicePixelRatio`
value, `OS.get_screen_dpi` uses CSS media queries to find approximate
DPI value for the current display.
`OS.get_screen_size` also return the actual screen size (not the CSS
pixel size).

1 files changed, 26 insertions, 0 deletions

diff --git a/platform/javascript/js/libs/library_godot_display.js b/platform/javascript/js/libs/library_godot_display.js
index 7b085aebc8..9ec295b39f 100644
--- a/platform/javascript/js/libs/library_godot_display.js
+++ b/platform/javascript/js/libs/library_godot_display.js
@@ -405,6 +405,27 @@ const GodotDisplay = {
 	$GodotDisplay__deps: ['$GodotConfig', '$GodotRuntime', '$GodotDisplayCursor', '$GodotDisplayListeners', '$GodotDisplayDragDrop', '$GodotDisplayGamepads'],
 	$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;
+			}
+		},
 	},
 
 	godot_js_display_is_swap_ok_cancel__sig: 'i',
@@ -422,6 +443,11 @@ const GodotDisplay = {
 		window.alert(GodotRuntime.parseString(p_text)); // eslint-disable-line no-alert
 	},
 
+	godot_js_display_screen_dpi_get__sig: 'i',
+	godot_js_display_screen_dpi_get: function () {
+		return GodotDisplay.findDPI();
+	},
+
 	godot_js_display_pixel_ratio_get__sig: 'f',
 	godot_js_display_pixel_ratio_get: function () {
 		return window.devicePixelRatio || 1;