kwin: Add WindowQuadList::makeInterleavedArrays()

Unlike makeArrays() this function writes into a pre-allocated array,
and takes a matrix that's used to transform the texture coordinates.
This allows this function to handle coordinates for rectangular
textures correctly.

libkwineffects/kwineffects.cpp

@@ -1046,6 +1046,38 @@ WindowQuadList WindowQuadList::makeRegularGrid(int xSubdivisions, int ySubdivisi
     return ret;
 }
 
+void WindowQuadList::makeInterleavedArrays(GLVertex2D *vertices, const QMatrix4x4 &textureMatrix) const
+{
+    // Since we know that the texture matrix just scales and translates
+    // we can use this information to optimize the transformation
+    const QVector2D coeff(textureMatrix(0, 0), textureMatrix(1, 1));
+    const QVector2D offset(textureMatrix(0, 3), textureMatrix(1, 3));
+
+    GLVertex2D *vertex = vertices;
+
+    for (int i = 0; i < count(); i++) {
+        const WindowQuad &quad = at(i);
+        GLVertex2D v[4]; // Four unique vertices / quad
+
+        for (int j = 0; j < 4; j++) {
+            const WindowVertex &wv = quad[j];
+
+            v[j].position = QVector2D(wv.x(), wv.y());
+            v[j].texcoord = QVector2D(wv.u(), wv.v()) * coeff + offset;
+        }
+
+        // First triangle
+        *(vertex++) = v[1]; // Top-right
+        *(vertex++) = v[0]; // Top-left
+        *(vertex++) = v[3]; // Bottom-left
+
+        // Second triangle
+        *(vertex++) = v[3]; // Bottom-left
+        *(vertex++) = v[2]; // Bottom-right
+        *(vertex++) = v[1]; // Top-right
+    }
+}
+
 void WindowQuadList::makeArrays(float **vertices, float **texcoords, const QSizeF &size, bool yInverted) const
 {
     *vertices = new float[count() * 6 * 2];

libkwineffects/kwineffects.h

@@ -30,6 +30,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QSet>
 #include <QRect>
 #include <QtGui/QRegion>
+#include <QtGui/QVector2D>
+#include <QtGui/QVector3D>
 
 #include <QVector>
 #include <QList>
@@ -49,7 +51,7 @@ class KActionCollection;
 class QFont;
 class QGraphicsScale;
 class QKeyEvent;
-class QVector2D;
+class QMatrix4x4;
 
 namespace KWin
 {
@@ -1664,6 +1666,20 @@ public:
     explicit GlobalShortcutsEditor(QWidget *parent);
 };
 
+
+struct GLVertex2D
+{
+    QVector2D position;
+    QVector2D texcoord;
+};
+
+struct GLVertex3D
+{
+    QVector3D position;
+    QVector2D texcoord;
+};
+
+
 /**
  * @short Vertex class
  *
@@ -1741,6 +1757,7 @@ public:
     WindowQuadList select(WindowQuadType type) const;
     WindowQuadList filterOut(WindowQuadType type) const;
     bool smoothNeeded() const;
+    void makeInterleavedArrays(GLVertex2D *vertices, const QMatrix4x4 &matrix) const;
     void makeArrays(float** vertices, float** texcoords, const QSizeF &size, bool yInverted) const;
     bool isTransformed() const;
 };