Squeeze labels on ES2

If the label text with slightly smaller font would fit into smaller
texture, force to use the smaller one.

Task-number: QTRD-3395
Change-Id: Ib70f6722ea8403e4aa25ed190b21c059d9d0e062
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@theqtcompany.com>
Reviewed-by: Tomi Korpipää <tomi.korpipaa@digia.com>

3 files changed, 28 insertions, 10 deletions

diff --git a/src/datavisualization/utils/texturehelper.cpp b/src/datavisualization/utils/texturehelper.cpp
index 2c40eb6a..939ce901 100644
--- a/src/datavisualization/utils/texturehelper.cpp
+++ b/src/datavisualization/utils/texturehelper.cpp
@@ -59,9 +59,8 @@ GLuint TextureHelper::create2DTexture(const QImage &image, bool useTrilinearFilt
     QImage texImage = image;
 
 #if defined(QT_OPENGL_ES_2)
-    GLuint temp;
-    GLuint imageWidth = Utils::getNearestPowerOfTwo(image.width(), temp);
-    GLuint imageHeight = Utils::getNearestPowerOfTwo(image.height(), temp);
+    GLuint imageWidth = Utils::getNearestPowerOfTwo(image.width());
+    GLuint imageHeight = Utils::getNearestPowerOfTwo(image.height());
     if (smoothScale) {
         texImage = image.scaled(imageWidth, imageHeight, Qt::IgnoreAspectRatio,
                                 Qt::SmoothTransformation);
diff --git a/src/datavisualization/utils/utils.cpp b/src/datavisualization/utils/utils.cpp
index 2767451e..534c79f9 100644
--- a/src/datavisualization/utils/utils.cpp
+++ b/src/datavisualization/utils/utils.cpp
@@ -27,11 +27,10 @@ QT_BEGIN_NAMESPACE_DATAVISUALIZATION
 
 static GLint maxTextureSize = 0; // Safe, as all instances have the same texture size
 
-GLuint Utils::getNearestPowerOfTwo(GLuint value, GLuint &padding)
+GLuint Utils::getNearestPowerOfTwo(GLuint value)
 {
     GLuint powOfTwoValue = MIN_POWER;
     NUM_IN_POWER(powOfTwoValue, value);
-    padding = powOfTwoValue - value;
     return powOfTwoValue;
 }
 
@@ -60,7 +59,9 @@ QImage Utils::printTextToImage(const QFont &font, const QString &text, const QCo
         glGetIntegerv(GL_MAX_TEXTURE_SIZE, &maxTextureSize);
 
     GLuint paddingWidth = 20;
+#if !defined(QT_OPENGL_ES_2) // TODO fix ifdef for dynamic OpenGL
     GLuint paddingHeight = 20;
+#endif
     // Calculate text dimensions
     QFont valueFont = font;
     valueFont.setPointSize(textureFontSize);
@@ -78,23 +79,41 @@ QImage Utils::printTextToImage(const QFont &font, const QString &text, const QCo
     QSize labelSize;
     qreal fontRatio = 1.0;
 
+#if defined(QT_OPENGL_ES_2) // TODO fix ifdef for dynamic OpenGL
+    // Test if text with slighly smaller font would fit into one step smaller texture
+    // ie. if the text is just exceeded the smaller texture boundary, it would
+    // make a label with large empty space
+    GLuint prePadding = 20;
+    GLint targetWidth = maxTextureSize;
+    uint testWidth = getNearestPowerOfTwo(valueStrWidth + prePadding) >> 1;
+    int diffToFit = (valueStrWidth + prePadding) - testWidth;
+    int maxSqueeze = int((valueStrWidth + prePadding) * 0.1f);
+    if (diffToFit < maxSqueeze && maxTextureSize > GLint(testWidth))
+        targetWidth = testWidth;
+#endif
+
     bool sizeOk = false;
     int currentFontSize = textureFontSize;
     do {
-#if defined(QT_OPENGL_ES_2)
+#if defined(QT_OPENGL_ES_2) // TODO fix ifdef for dynamic OpenGL
         // ES2 can't handle textures with dimensions not in power of 2. Resize labels accordingly.
         // Add some padding before converting to power of two to avoid too tight fit
-        GLuint prePadding = 5;
         labelSize = QSize(valueStrWidth + prePadding, valueStrHeight + prePadding);
-        labelSize.setWidth(getNearestPowerOfTwo(labelSize.width(), paddingWidth));
-        labelSize.setHeight(getNearestPowerOfTwo(labelSize.height(), paddingHeight));
+        labelSize.setWidth(getNearestPowerOfTwo(labelSize.width()));
+        labelSize.setHeight(getNearestPowerOfTwo(labelSize.height()));
 #else
         if (!labelBackground)
             labelSize = QSize(valueStrWidth, valueStrHeight);
         else
             labelSize = QSize(valueStrWidth + paddingWidth * 2, valueStrHeight + paddingHeight * 2);
 #endif
+
+#if defined(QT_OPENGL_ES_2)
+        if (!maxTextureSize || (labelSize.width() <= maxTextureSize
+                                && labelSize.width() <= targetWidth)) {
+#else
         if (!maxTextureSize || labelSize.width() <= maxTextureSize) {
+#endif
             // Make sure the label is not too wide
             sizeOk = true;
         } else if (--currentFontSize == 4) {
diff --git a/src/datavisualization/utils/utils_p.h b/src/datavisualization/utils/utils_p.h
index 805c41a7..fdcb0da0 100644
--- a/src/datavisualization/utils/utils_p.h
+++ b/src/datavisualization/utils/utils_p.h
@@ -45,7 +45,7 @@ public:
         ParamTypeReal
     };
 
-    static GLuint getNearestPowerOfTwo(GLuint value, GLuint &padding);
+    static GLuint getNearestPowerOfTwo(GLuint value);
     static QVector4D vectorFromColor(const QColor &color);
     static QColor colorFromVector(const QVector3D &colorVector);
     static QColor colorFromVector(const QVector4D &colorVector);