Disable depth testing during the 2D QGLWidget::renderText()

Also document the depth testing conditions for the 2D and 3D
versions of the function.

Task-number: QTBUG-5041
Reviewed-by: Daniel Pope

1 files changed, 12 insertions, 0 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 32534aa..466e851 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -4302,6 +4302,7 @@ static void qt_save_gl_state()
     glDisable(GL_CULL_FACE);
     glDisable(GL_LIGHTING);
     glDisable(GL_STENCIL_TEST);
+    glDisable(GL_DEPTH_TEST);
     glEnable(GL_BLEND);
     glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
 }
@@ -4355,6 +4356,10 @@ static void qt_gl_draw_text(QPainter *p, int x, int y, const QString &str,
    \note This function clears the stencil buffer.
 
    \note This function is not supported on OpenGL/ES systems.
+
+   \note This function temporarily disables depth-testing when the
+   text is drawn.
+
    \l{Overpainting Example}{Overpaint} with QPainter::drawText() instead.
 */
 
@@ -4445,6 +4450,13 @@ void QGLWidget::renderText(int x, int y, const QString &str, const QFont &font,
     have the labels move with the model as it is rotated etc.
 
     \note This function is not supported on OpenGL/ES systems.
+
+    \note If depth testing is enabled before this function is called,
+    then the drawn text will be depth-tested against the models that
+    have already been drawn in the scene.  Use \c{glDisable(GL_DEPTH_TEST)}
+    before calling this function to annotate the models without
+    depth-testing the text.
+
     \l{Overpainting Example}{Overpaint} with QPainter::drawText() instead.
 */
 void QGLWidget::renderText(double x, double y, double z, const QString &str, const QFont &font, int)