Examples/OpenGLWindow: do not use hardcoded indices

Don't use the hardcoded indices 0 and 1 but the ones returned from
QOpenGLShaderProgram::attributeLocation(). Also change them from GLuint
to GLint.

Fixes: QTBUG-43566
Change-Id: I582bcf899f20d90f4ec1cd61326a177aabb69992
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 14 insertions, 11 deletions

diff --git a/examples/gui/openglwindow/main.cpp b/examples/gui/openglwindow/main.cpp
index d1e5d3871e..03a6ece06f 100644
--- a/examples/gui/openglwindow/main.cpp
+++ b/examples/gui/openglwindow/main.cpp
@@ -67,9 +67,9 @@ public:
     void render() override;
 
 private:
-    GLuint m_posAttr = 0;
-    GLuint m_colAttr = 0;
-    GLuint m_matrixUniform = 0;
+    GLint m_posAttr = 0;
+    GLint m_colAttr = 0;
+    GLint m_matrixUniform = 0;
 
     QOpenGLShaderProgram *m_program = nullptr;
     int m_frame = 0;
@@ -122,8 +122,11 @@ void TriangleWindow::initialize()
     m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);
     m_program->link();
     m_posAttr = m_program->attributeLocation("posAttr");
+    Q_ASSERT(m_posAttr != -1);
     m_colAttr = m_program->attributeLocation("colAttr");
+    Q_ASSERT(m_colAttr != -1);
     m_matrixUniform = m_program->uniformLocation("matrix");
+    Q_ASSERT(m_matrixUniform != -1);
 }
 //! [4]
 
@@ -144,13 +147,13 @@ void TriangleWindow::render()
 
     m_program->setUniformValue(m_matrixUniform, matrix);
 
-    GLfloat vertices[] = {
-        0.0f, 0.707f,
+    static const GLfloat vertices[] = {
+         0.0f,  0.707f,
         -0.5f, -0.5f,
-        0.5f, -0.5f
+         0.5f, -0.5f
     };
 
-    GLfloat colors[] = {
+    static const GLfloat colors[] = {
         1.0f, 0.0f, 0.0f,
         0.0f, 1.0f, 0.0f,
         0.0f, 0.0f, 1.0f
@@ -159,13 +162,13 @@ void TriangleWindow::render()
     glVertexAttribPointer(m_posAttr, 2, GL_FLOAT, GL_FALSE, 0, vertices);
     glVertexAttribPointer(m_colAttr, 3, GL_FLOAT, GL_FALSE, 0, colors);
 
-    glEnableVertexAttribArray(0);
-    glEnableVertexAttribArray(1);
+    glEnableVertexAttribArray(m_posAttr);
+    glEnableVertexAttribArray(m_colAttr);
 
     glDrawArrays(GL_TRIANGLES, 0, 3);
 
-    glDisableVertexAttribArray(1);
-    glDisableVertexAttribArray(0);
+    glDisableVertexAttribArray(m_colAttr);
+    glDisableVertexAttribArray(m_posAttr);
 
     m_program->release();