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Improve support for High DPI displays

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On high DPI displays, a logical pixel does not necessarily equal a
device pixel. Images and such are scaled up to the logical pixel size;
unfortunately this introduces ugly aliasing. Web pages can take
advantage of high DPI screens by intentionally scaling stuff down to be
displayed at a higher resolution. By carefully canceling out the
automatic scaling of the game canvas we get nice crisp pixels even on
high DPI screens.

See the pull request for before/after screenshots.
This commit is contained in:
Andrew Ekstedt 2020-09-10 20:07:54 -07:00
parent d3e60b88fa
commit f0f2259aa1
1 changed files with 11 additions and 2 deletions
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13
js/main.js
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@ -619,18 +619,27 @@ class Player extends PrimaryView {
// The main UI is centered in a flex item with auto margins, so the
// extra space available is the size of those margins
let style = window.getComputedStyle(this.root);
if (style['display'] === 'none') {
// the computed margins can be 'auto' in this case
return;
}
let extra_x = parseFloat(style['margin-left']) + parseFloat(style['margin-right']);
let extra_y = parseFloat(style['margin-top']) + parseFloat(style['margin-bottom']);
// The total available space, then, is the current size of the
// canvas plus the size of the margins
let total_x = extra_x + this.renderer.canvas.offsetWidth;
let total_y = extra_y + this.renderer.canvas.offsetHeight;
let dpr = window.devicePixelRatio || 1.0;
// Divide to find the biggest scale that still fits. But don't
// exceed 90% of the available space, or it'll feel cramped.
let scale = Math.floor(0.9 * Math.min(total_x / base_x, total_y / base_y));
if (scale <= 0) {
let scale = Math.floor(0.9 * dpr * Math.min(total_x / base_x, total_y / base_y));
if (scale <= 1) {
scale = 1;
}
// High DPI support: scale the canvas down by the inverse of the device
// pixel ratio, thus matching the canvas's resolution to the screen
// resolution and giving us nice, clean pixels.
scale /= dpr;
// FIXME the above logic doesn't take into account the inventory, which is also affected by scale
this.scale = scale;