Speed up QStaticText with affine transformation on GL2 engine

Since the OpenGL2 paint engine supports transforming the prerendered
glyphs rather than rasterizing the glyphs with the transformation
applied, we don't need to recalculate the QStaticText layout whenever
the transformation changes. This means that we can do fast animated
transforms for QStaticText on this paint engine. A quick test yields
something like 100x speed-up on Windows. This also give visually
better results, as we previously would animate the hinting of the
glyphs, thus causing jittering.

The autotest has been updated to reflect the fact that drawText() and
drawStaticText() now go through identical paths on GL, also when
transforms are set on the painter. However, the scale was changed in
one test, because it was so great that drawText() would fall back to
paths. With QStaticText the idea is speed, so you'll get a poor, but
fast result instead, which is better than tricking people.

Reviewed-by: Samuel

1 files changed, 17 insertions, 6 deletions

diff --git a/src/gui/painting/qpainter.cpp b/src/gui/painting/qpainter.cpp
index 657229a..4596754 100644
--- a/src/gui/painting/qpainter.cpp
+++ b/src/gui/painting/qpainter.cpp
@@ -5855,14 +5855,24 @@ void QPainter::drawStaticText(const QPointF &topLeftPosition, const QStaticText
         return;
     }
 
+    if (d->extended->type() == QPaintEngine::OpenGL2 && !staticText_d->untransformedCoordinates) {
+        staticText_d->untransformedCoordinates = true;
+        staticText_d->needsRelayout = true;
+    } else if (d->extended->type() != QPaintEngine::OpenGL2 && staticText_d->untransformedCoordinates) {
+        staticText_d->untransformedCoordinates = false;
+        staticText_d->needsRelayout = true;
+    }
+
     // Don't recalculate entire layout because of translation, rather add the dx and dy
     // into the position to move each text item the correct distance.
-    QPointF transformedPosition = topLeftPosition * d->state->matrix;
-    QTransform matrix = d->state->matrix;
+    QPointF transformedPosition = topLeftPosition;
+    if (!staticText_d->untransformedCoordinates)
+        transformedPosition = transformedPosition * d->state->matrix;
+    QTransform oldMatrix;
 
     // The translation has been applied to transformedPosition. Remove translation
     // component from matrix.
-    if (d->state->matrix.isTranslating()) {
+    if (d->state->matrix.isTranslating() && !staticText_d->untransformedCoordinates) {
         qreal m11 = d->state->matrix.m11();
         qreal m12 = d->state->matrix.m12();
         qreal m13 = d->state->matrix.m13();
@@ -5871,6 +5881,7 @@ void QPainter::drawStaticText(const QPointF &topLeftPosition, const QStaticText
         qreal m23 = d->state->matrix.m23();
         qreal m33 = d->state->matrix.m33();
 
+        oldMatrix = d->state->matrix;
         d->state->matrix.setMatrix(m11, m12, m13,
                                    m21, m22, m23,
                                    0.0, 0.0, m33);
@@ -5879,7 +5890,7 @@ void QPainter::drawStaticText(const QPointF &topLeftPosition, const QStaticText
     // If the transform is not identical to the text transform,
     // we have to relayout the text (for other transformations than plain translation)
     bool staticTextNeedsReinit = staticText_d->needsRelayout;
-    if (staticText_d->matrix != d->state->matrix) {
+    if (!staticText_d->untransformedCoordinates && staticText_d->matrix != d->state->matrix) {
         staticText_d->matrix = d->state->matrix;
         staticTextNeedsReinit = true;
     }
@@ -5918,8 +5929,8 @@ void QPainter::drawStaticText(const QPointF &topLeftPosition, const QStaticText
     if (currentColor != oldPen.color())
         setPen(oldPen);
 
-    if (matrix.isTranslating())
-        d->state->matrix = matrix;
+    if (!staticText_d->untransformedCoordinates && oldMatrix.isTranslating())
+        d->state->matrix = oldMatrix;
 }
 
 /*!