Add support for GL_ARB_texture_storage

Use glTexStorage2D() to allocate storage for the texture. The structure
of the resulting texture becomes immutable and the texture is always
mipmap complete.  This allows the driver to skip the mipmap consistency
checks when validating the texture at draw time.

libkwineffects/kwingltexture.cpp

@@ -45,6 +45,7 @@ namespace KWin
 bool GLTexturePrivate::s_supportsFramebufferObjects = false;
 bool GLTexturePrivate::s_supportsARGB32 = false;
 bool GLTexturePrivate::s_supportsUnpack = false;
+bool GLTexturePrivate::s_supportsTextureStorage = false;
 uint GLTexturePrivate::s_textureObjectCounter = 0;
 uint GLTexturePrivate::s_fbo = 0;
 
@@ -94,9 +95,17 @@ GLTexture::GLTexture(const QImage& image, GLenum target)
 
     if (!GLPlatform::instance()->isGLES()) {
         const QImage im = image.convertToFormat(QImage::Format_ARGB32_Premultiplied);
-        glTexParameteri(d->m_target, GL_TEXTURE_MAX_LEVEL, d->m_mipLevels - 1);
-        glTexImage2D(d->m_target, 0, GL_RGBA8, im.width(), im.height(), 0,
-                     GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, im.bits());
+
+        if (d->s_supportsTextureStorage) {
+            glTexStorage2D(d->m_target, 1, GL_RGBA8, im.width(), im.height());
+            glTexSubImage2D(d->m_target, 0, 0, 0, im.width(), im.height(),
+                            GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, im.bits());
+            d->m_immutable = true;
+        } else {
+            glTexParameteri(d->m_target, GL_TEXTURE_MAX_LEVEL, d->m_mipLevels - 1);
+            glTexImage2D(d->m_target, 0, GL_RGBA8, im.width(), im.height(), 0,
+                         GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, im.bits());
+        }
     } else {
         if (d->s_supportsARGB32) {
             const QImage im = image.convertToFormat(QImage::Format_ARGB32_Premultiplied);
@@ -143,9 +152,14 @@ GLTexture::GLTexture(int width, int height, int levels)
     bind();
 
     if (!GLPlatform::instance()->isGLES()) {
-        glTexParameteri(d->m_target, GL_TEXTURE_MAX_LEVEL, levels - 1);
-        glTexImage2D(d->m_target, 0, GL_RGBA8, width, height, 0,
-                     GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, nullptr);
+        if (d->s_supportsTextureStorage) {
+            glTexStorage2D(d->m_target, levels, GL_RGBA8, width, height);
+            d->m_immutable = true;
+        } else {
+            glTexParameteri(d->m_target, GL_TEXTURE_MAX_LEVEL, levels - 1);
+            glTexImage2D(d->m_target, 0, GL_RGBA8, width, height, 0,
+                         GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, nullptr);
+        }
     } else {
         // The format parameter in glTexSubImage() must match the internal format
         // of the texture, so it's important that we allocate the texture with
@@ -182,6 +196,7 @@ GLTexturePrivate::GLTexturePrivate()
     m_yInverted = false;
     m_canUseMipmaps = false;
     m_mipLevels = 1;
+    m_immutable = false;
     m_markedDirty = false;
     m_unnormalizeActive = 0;
     m_normalizeActive = 0;
@@ -211,10 +226,12 @@ void GLTexturePrivate::initStatic()
     if (!GLPlatform::instance()->isGLES()) {
         s_supportsFramebufferObjects = hasGLVersion(3, 0) ||
             hasGLExtension("GL_ARB_framebuffer_object") || hasGLExtension(QByteArrayLiteral("GL_EXT_framebuffer_object"));
+        s_supportsTextureStorage = hasGLVersion(4, 2) || hasGLExtension(QByteArrayLiteral("GL_ARB_texture_storage"));
         s_supportsARGB32 = true;
         s_supportsUnpack = true;
     } else {
         s_supportsFramebufferObjects = true;
+        s_supportsTextureStorage = hasGLVersion(3, 0) || hasGLExtension(QByteArrayLiteral("GL_EXT_texture_storage"));
 
         // QImage::Format_ARGB32_Premultiplied is a packed-pixel format, so it's only
         // equivalent to GL_BGRA/GL_UNSIGNED_BYTE on little-endian systems.

libkwineffects/kwingltexture_p.h

@@ -58,6 +58,7 @@ public:
     bool m_markedDirty;
     bool m_filterChanged;
     bool m_wrapModeChanged;
+    bool m_immutable;
     int m_mipLevels;
 
     int m_unnormalizeActive; // 0 - no, otherwise refcount
@@ -70,6 +71,7 @@ public:
     static bool s_supportsFramebufferObjects;
     static bool s_supportsARGB32;
     static bool s_supportsUnpack;
+    static bool s_supportsTextureStorage;
     static GLuint s_fbo;
     static uint s_textureObjectCounter;
 private: