From: =?utf-8?b?Ik1hcmNvIFRyZXZpc2FuIChUcmV2acOxbyki?= <mail@3v1n0.net>
Date: Wed, 27 Mar 2019 16:14:39 +0100
Subject: magnifier: Scale the sprite to match the current monitor scaling

Compute the sprite texture scale (unfortunately using a workaround, based on
mutter cursor size preferences, tying to figure out the closest texture integer
scaling), and use this value to compute the scaling that should be applied to
the sprite in order to match the current monitor scaling.

Origin: https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/475
Applied-Upstream: no
Forwarded: yes
---
 js/ui/layout.js    | 24 ++++++++++++++++++++----
 js/ui/magnifier.js | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 73 insertions(+), 6 deletions(-)

diff --git a/js/ui/layout.js b/js/ui/layout.js
index 3ba9b96..4d5cd5a 100644
--- a/js/ui/layout.js
+++ b/js/ui/layout.js
@@ -981,22 +981,38 @@ export const LayoutManager = GObject.registerClass({
         return ws.get_work_area_for_monitor(monitorIndex);
     }
 
+    _findIndexForRect(x, y, width, height) {
+        const rect = new Mtk.Rectangle({
+            x: Math.floor(x),
+            y: Math.floor(y),
+            width: Math.ceil(x + width) - Math.floor(x),
+            height: Math.ceil(y + height) - Math.floor(y),
+        });
+        return global.display.get_monitor_index_for_rect(rect);
+    }
+
     // This call guarantees that we return some monitor to simplify usage of it
     // In practice all tracked actors should be visible on some monitor anyway
     findIndexForActor(actor) {
         let [x, y] = actor.get_transformed_position();
         let [w, h] = actor.get_transformed_size();
-        const rect = new Mtk.Rectangle({x, y, width: w, height: h});
-        return global.display.get_monitor_index_for_rect(rect);
+        return this._findIndexForRect(x, y, w, h);
     }
 
-    findMonitorForActor(actor) {
-        let index = this.findIndexForActor(actor);
+    _findMonitorForIndex(index) {
         if (index >= 0 && index < this.monitors.length)
             return this.monitors[index];
         return null;
     }
 
+    findMonitorForActor(actor) {
+        return this._findMonitorForIndex(this.findIndexForActor(actor));
+    }
+
+    findMonitorForPoint(x, y) {
+        return this._findMonitorForIndex(this._findIndexForRect(x, y, 1, 1));
+    }
+
     _queueUpdateRegions() {
         if (!this._updateRegionIdle) {
             const laters = global.compositor.get_laters();
diff --git a/js/ui/magnifier.js b/js/ui/magnifier.js
index ab8150b..13da38f 100644
--- a/js/ui/magnifier.js
+++ b/js/ui/magnifier.js
@@ -51,6 +51,8 @@ const MouseSpriteContent = GObject.registerClass({
 }, class MouseSpriteContent extends GObject.Object {
     _init() {
         super._init();
+        this._scale = 1.0;
+        this._monitorScale = 1.0;
         this._texture = null;
     }
 
@@ -58,7 +60,10 @@ const MouseSpriteContent = GObject.registerClass({
         if (!this._texture)
             return [false, 0, 0];
 
-        return [true, this._texture.get_width(), this._texture.get_height()];
+        let width = this._texture.get_width() / this._scale;
+        let height = this._texture.get_height() / this._scale;
+
+        return [true, width, height];
     }
 
     vfunc_paint_content(actor, node, _paintContext) {
@@ -75,6 +80,29 @@ const MouseSpriteContent = GObject.registerClass({
         textureNode.add_rectangle(actor.get_content_box());
     }
 
+    _textureScale() {
+        if (!this._texture)
+            return 1;
+
+        /* This is a workaround to guess the sprite scale; while it works file
+         * in normal scenarios, it's not guaranteed to work in all the cases,
+         * and so we should actually add an API to mutter that will allow us
+         * to know the real spirte texture scaling in order to adapt it to the
+         * wanted one. */
+        let avgSize = (this._texture.get_width() + this._texture.get_height()) / 2;
+        return Math.max(1, Math.floor(avgSize / Meta.prefs_get_cursor_size() + .1));
+    }
+
+    _recomputeScale() {
+        let scale = this._textureScale() / this._monitorScale;
+
+        if (this._scale !== scale) {
+            this._scale = scale;
+            return true;
+        }
+        return false;
+    }
+
     get texture() {
         return this._texture;
     }
@@ -89,7 +117,19 @@ const MouseSpriteContent = GObject.registerClass({
 
         if (!oldTexture || !coglTexture ||
             oldTexture.get_width() !== coglTexture.get_width() ||
-            oldTexture.get_height() !== coglTexture.get_height())
+            oldTexture.get_height() !== coglTexture.get_height()) {
+            this._recomputeScale();
+            this.invalidate_size();
+        }
+    }
+
+    get scale() {
+        return this._scale;
+    }
+
+    set monitorScale(monitorScale) {
+        this._monitorScale = monitorScale;
+        if (this._recomputeScale())
             this.invalidate_size();
     }
 });
@@ -121,6 +161,8 @@ export class Magnifier extends Signals.EventEmitter {
         this._settingsInit(aZoomRegion);
         aZoomRegion.scrollContentsTo(this.xMouse, this.yMouse);
 
+        this._updateContentScale();
+
         St.Settings.get().connect('notify::magnifier-active', () => {
             this.setActive(St.Settings.get().magnifier_active);
         });
@@ -128,6 +170,13 @@ export class Magnifier extends Signals.EventEmitter {
         this.setActive(St.Settings.get().magnifier_active);
     }
 
+    _updateContentScale() {
+        let monitor = Main.layoutManager.findMonitorForPoint(this.xMouse,
+            this.yMouse);
+        this._mouseSprite.content.monitorScale = monitor
+            ? monitor.geometry_scale : 1;
+    }
+
     /**
      * showSystemCursor:
      * Show the system mouse pointer.
@@ -269,6 +318,8 @@ export class Magnifier extends Signals.EventEmitter {
         this.xMouse = xMouse;
         this.yMouse = yMouse;
 
+        this._updateContentScale();
+
         let sysMouseOverAny = false;
         this._zoomRegions.forEach(zoomRegion => {
             if (zoomRegion.scrollToMousePos())