kwineffects: Allocate hidpi textures in DeformEffect

If a window is animated using DeformEffect, allocate an offscreen
texture with the scale factor of the screen where the window is
considered to be on.

Also, resize the offscreen texture on demand in order to make resource
handling more efficient.

src/libkwineffects/kwindeformeffect.cpp

@@ -22,7 +22,6 @@ class DeformEffectPrivate
 {
 public:
     QHash<EffectWindow *, DeformOffscreenData *> windows;
-    QMetaObject::Connection windowExpandedGeometryChangedConnection;
     QMetaObject::Connection windowDamagedConnection;
     QMetaObject::Connection windowDeletedConnection;
 
@@ -48,26 +47,13 @@ bool DeformEffect::supported()
     return effects->isOpenGLCompositing();
 }
 
-static void allocateOffscreenData(EffectWindow *window, DeformOffscreenData *offscreenData)
-{
-    const QRect geometry = window->expandedGeometry();
-    offscreenData->texture.reset(new GLTexture(GL_RGBA8, geometry.size()));
-    offscreenData->texture->setFilter(GL_LINEAR);
-    offscreenData->texture->setWrapMode(GL_CLAMP_TO_EDGE);
-    offscreenData->renderTarget.reset(new GLRenderTarget(*offscreenData->texture));
-    offscreenData->isDirty = true;
-}
-
 void DeformEffect::redirect(EffectWindow *window)
 {
     DeformOffscreenData *&offscreenData = d->windows[window];
     if (offscreenData) {
         return;
     }
-
-    effects->makeOpenGLContextCurrent();
     offscreenData = new DeformOffscreenData;
-    allocateOffscreenData(window, offscreenData);
 
     if (d->windows.count() == 1) {
         setupConnections();
@@ -92,12 +78,26 @@ void DeformEffect::deform(EffectWindow *window, int mask, WindowPaintData &data,
 
 GLTexture *DeformEffectPrivate::maybeRender(EffectWindow *window, DeformOffscreenData *offscreenData)
 {
+    const QRect geometry = window->expandedGeometry();
+    QSize textureSize = geometry.size();
+
+    if (const EffectScreen *screen = effects->findScreen(window->screen())) {
+        textureSize *= screen->devicePixelRatio();
+    }
+
+    if (!offscreenData->texture || offscreenData->texture->size() != textureSize) {
+        offscreenData->texture.reset(new GLTexture(GL_RGBA8, textureSize));
+        offscreenData->texture->setFilter(GL_LINEAR);
+        offscreenData->texture->setWrapMode(GL_CLAMP_TO_EDGE);
+        offscreenData->renderTarget.reset(new GLRenderTarget(*offscreenData->texture));
+        offscreenData->isDirty = true;
+    }
+
     if (offscreenData->isDirty) {
         GLRenderTarget::pushRenderTarget(offscreenData->renderTarget.data());
         glClearColor(0.0, 0.0, 0.0, 0.0);
         glClear(GL_COLOR_BUFFER_BIT);
 
-        const QRect geometry = window->expandedGeometry();
         QMatrix4x4 projectionMatrix;
         projectionMatrix.ortho(QRect(0, 0, geometry.width(), geometry.height()));
 
@@ -190,18 +190,6 @@ void DeformEffect::drawWindow(EffectWindow *window, int mask, const QRegion& reg
     d->paint(window, texture, region, data, quads);
 }
 
-void DeformEffect::handleWindowGeometryChanged(EffectWindow *window)
-{
-    DeformOffscreenData *offscreenData = d->windows.value(window);
-    if (offscreenData) {
-        const QRect geometry = window->expandedGeometry();
-        if (offscreenData->texture->size() != geometry.size()) {
-            effects->makeOpenGLContextCurrent();
-            allocateOffscreenData(window, offscreenData);
-        }
-    }
-}
-
 void DeformEffect::handleWindowDamaged(EffectWindow *window)
 {
     DeformOffscreenData *offscreenData = d->windows.value(window);
@@ -217,8 +205,6 @@ void DeformEffect::handleWindowDeleted(EffectWindow *window)
 
 void DeformEffect::setupConnections()
 {
-    d->windowExpandedGeometryChangedConnection =
-            connect(effects, &EffectsHandler::windowExpandedGeometryChanged, this, &DeformEffect::handleWindowGeometryChanged);
     d->windowDamagedConnection =
             connect(effects, &EffectsHandler::windowDamaged, this, &DeformEffect::handleWindowDamaged);
     d->windowDeletedConnection =
@@ -227,11 +213,9 @@ void DeformEffect::setupConnections()
 
 void DeformEffect::destroyConnections()
 {
-    disconnect(d->windowExpandedGeometryChangedConnection);
     disconnect(d->windowDamagedConnection);
     disconnect(d->windowDeletedConnection);
 
-    d->windowExpandedGeometryChangedConnection = {};
     d->windowDamagedConnection = {};
     d->windowDeletedConnection = {};
 }

src/libkwineffects/kwindeformeffect.h

@@ -58,7 +58,6 @@ protected:
     virtual void deform(EffectWindow *window, int mask, WindowPaintData &data, WindowQuadList &quads);
 
 private Q_SLOTS:
-    void handleWindowGeometryChanged(EffectWindow *window);
     void handleWindowDamaged(EffectWindow *window);
     void handleWindowDeleted(EffectWindow *window);