Fix: bad-looking scaled rendering of painterpath in OpenGL paint engine

For performance, the triangulation of a painter path is stored for
reuse. Re-triangulation was only done if the path was to be painted at
a significantly different scale AND it contained a curve (bezier)
element. But also the triangulation of a path with only straight lines
can lose precision if rendered at a small scale, and so look bad when
used at a higher scale factor.

Fix by removing the mentioned curve element condition.

Task-number: QTBUG-68873
Change-Id: Id3492514e9382a5828377b7bafea8cfac7b850a6
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 17 insertions, 21 deletions

diff --git a/src/gui/opengl/qopenglpaintengine.cpp b/src/gui/opengl/qopenglpaintengine.cpp
index 17dc9df619..3d1c362275 100644
--- a/src/gui/opengl/qopenglpaintengine.cpp
+++ b/src/gui/opengl/qopenglpaintengine.cpp
@@ -797,20 +797,18 @@ void QOpenGL2PaintEngineExPrivate::fill(const QVectorPath& path)
 
             if (data) {
                 cache = (QOpenGL2PEVectorPathCache *) data->data;
-                // Check if scale factor is exceeded for curved paths and generate curves if so...
-                if (path.isCurved()) {
-                    qreal scaleFactor = cache->iscale / inverseScale;
-                    if (scaleFactor < 0.5 || scaleFactor > 2.0) {
+                // Check if scale factor is exceeded and regenerate if so...
+                qreal scaleFactor = cache->iscale / inverseScale;
+                if (scaleFactor < 0.5 || scaleFactor > 2.0) {
 #ifdef QT_OPENGL_CACHE_AS_VBOS
-                        glDeleteBuffers(1, &cache->vbo);
-                        cache->vbo = 0;
-                        Q_ASSERT(cache->ibo == 0);
+                    glDeleteBuffers(1, &cache->vbo);
+                    cache->vbo = 0;
+                    Q_ASSERT(cache->ibo == 0);
 #else
-                        free(cache->vertices);
-                        Q_ASSERT(cache->indices == 0);
+                    free(cache->vertices);
+                    Q_ASSERT(cache->indices == 0);
 #endif
-                        updateCache = true;
-                    }
+                    updateCache = true;
                 }
             } else {
                 cache = new QOpenGL2PEVectorPathCache;
@@ -879,19 +877,17 @@ void QOpenGL2PaintEngineExPrivate::fill(const QVectorPath& path)
 
             if (data) {
                 cache = (QOpenGL2PEVectorPathCache *) data->data;
-                // Check if scale factor is exceeded for curved paths and generate curves if so...
-                if (path.isCurved()) {
-                    qreal scaleFactor = cache->iscale / inverseScale;
-                    if (scaleFactor < 0.5 || scaleFactor > 2.0) {
+                // Check if scale factor is exceeded and regenerate if so...
+                qreal scaleFactor = cache->iscale / inverseScale;
+                if (scaleFactor < 0.5 || scaleFactor > 2.0) {
 #ifdef QT_OPENGL_CACHE_AS_VBOS
-                        glDeleteBuffers(1, &cache->vbo);
-                        glDeleteBuffers(1, &cache->ibo);
+                    glDeleteBuffers(1, &cache->vbo);
+                    glDeleteBuffers(1, &cache->ibo);
 #else
-                        free(cache->vertices);
-                        free(cache->indices);
+                    free(cache->vertices);
+                    free(cache->indices);
 #endif
-                        updateCache = true;
-                    }
+                    updateCache = true;
                 }
             } else {
                 cache = new QOpenGL2PEVectorPathCache;