🎉 Start incinerate effect at pointer location

src/Incinerate.js

@@ -47,22 +47,65 @@ var Incinerate = class {
       shader._uColor      = shader.get_uniform_location('uColor');
       shader._uScale      = shader.get_uniform_location('uScale');
       shader._uTurbulence = shader.get_uniform_location('uTurbulence');
+      shader._uStartPos   = shader.get_uniform_location('uStartPos');
 
       // Write all uniform values at the start of each animation.
-      shader.connect('begin-animation', (shader, settings) => {
-        const c = Clutter.Color.from_string(settings.get_string('incinerate-color'))[1];
-
+      shader.connect('begin-animation', (shader, settings, forOpening, actor) => {
         // If we are currently performing integration test, the animation uses a fixed
         // seed.
         const testMode = settings.get_boolean('test-mode');
+        let seed       = [testMode ? 0 : Math.random(), testMode ? 0 : Math.random()];
+
+        // If this option is set, we use the mouse pointer position. Because the actor
+        // position may change after the begin-animation signal is called, we set the
+        // uStartPos uniform during the update callback.
+        if (settings.get_boolean('incinerate-use-pointer')) {
+          this._startPointerPos = global.get_pointer();
+          this._actor           = actor;
+
+        } else {
+          // Else, a random position along the window boundary is used as start position
+          // for the incinerate effect.
+          let startPos = seed[0] > seed[1] ? [seed[0], Math.floor(seed[1] + 0.5)] :
+                                             [Math.floor(seed[0] + 0.5), seed[1]];
+
+          shader.set_uniform_float(shader._uStartPos, 2, startPos);
+
+          this._startPointerPos = null;
+        }
+
+        const c = Clutter.Color.from_string(settings.get_string('incinerate-color'))[1];
 
         // clang-format off
-        shader.set_uniform_float(shader._uSeed,  2, [testMode ? 0 : Math.random(), testMode ? 0 : Math.random()]);
-        shader.set_uniform_float(shader._uColor, 3, [c.red / 255, c.green / 255, c.blue / 255]);
-        shader.set_uniform_float(shader._uScale, 1, [settings.get_double('incinerate-scale')]);
+        shader.set_uniform_float(shader._uSeed,       2, seed);
+        shader.set_uniform_float(shader._uColor,      3, [c.red / 255, c.green / 255, c.blue / 255]);
+        shader.set_uniform_float(shader._uScale,      1, [settings.get_double('incinerate-scale')]);
         shader.set_uniform_float(shader._uTurbulence, 1, [settings.get_double('incinerate-turbulence')]);
         // clang-format on
       });
+
+      // If the mouse pointer position is used as start position, we set the uStartPos
+      // uniform during the update callback as the actor position may not be set up
+      // properly before the begin animation callback.
+      shader.connect('update-animation', (shader) => {
+        if (this._startPointerPos) {
+          const [x, y]               = this._startPointerPos;
+          const [ok, localX, localY] = this._actor.transform_stage_point(x, y);
+
+          if (ok) {
+            let startPos = [
+              Math.max(0.0, Math.min(1.0, localX / this._actor.width)),
+              Math.max(0.0, Math.min(1.0, localY / this._actor.height))
+            ];
+            shader.set_uniform_float(shader._uStartPos, 2, startPos);
+          }
+        }
+      });
+
+      // Make sure to drop the reference to the actor.
+      shader.connect('end-animation', (shader) => {
+        shader._actor = null;
+      });
     });
   }
 
@@ -100,6 +143,7 @@ var Incinerate = class {
     dialog.bindAdjustment('incinerate-animation-time');
     dialog.bindAdjustment('incinerate-scale');
     dialog.bindAdjustment('incinerate-turbulence');
+    dialog.bindSwitch('incinerate-use-pointer');
     dialog.bindColorButton('incinerate-color');
 
     // Finally, return the new settings page.