Avoid repeated QByteArray creation when resolving opengl functions

Add an getProcAddress(const char *) overload to QOpenGLContext,
and refactor the QPA interface to take a const char *. Like this
we can avoid lots of mallocs when resoving GL methods.

Change-Id: Ic45b985fbaa0da8d32ba3e3b485351173352ca6f
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

1 files changed, 29 insertions, 26 deletions

diff --git a/src/gui/opengl/qopenglfunctions.cpp b/src/gui/opengl/qopenglfunctions.cpp
index b7a82a5def..b77f2c4f0f 100644
--- a/src/gui/opengl/qopenglfunctions.cpp
+++ b/src/gui/opengl/qopenglfunctions.cpp
@@ -2199,36 +2199,39 @@ private:
 
 static QFunctionPointer getProcAddress(QOpenGLContext *context, const char *funcName, int policy)
 {
-    QByteArray fn = funcName;
-    int size = fn.size();
-    QFunctionPointer function = context->getProcAddress(fn);
-
-    // create room for the extension names
-    fn.resize(size + 5);
-    char *ext = fn.data() + size;
-    if (!function && (policy & ResolveOES)) {
-        memcpy(ext, "OES\0\0", 5);
-        function = context->getProcAddress(fn);
-    }
+    QFunctionPointer function = context->getProcAddress(funcName);
+
+    if (!function && policy) {
+        char fn[512];
+        size_t size = strlen(funcName);
+        Q_ASSERT(size < 500);
+        memcpy(fn, funcName, size);
+
+        char *ext = fn + size;
+        if (!function && (policy & ResolveOES)) {
+            memcpy(ext, "OES", 4);
+            function = context->getProcAddress(fn);
+        }
 
-    if (!function) {
-        memcpy(ext, "ARB\0\0", 5);
-        function = context->getProcAddress(fn);
-    }
+        if (!function) {
+            memcpy(ext, "ARB", 4);
+            function = context->getProcAddress(fn);
+        }
 
-    if (!function && (policy & ResolveEXT)) {
-        memcpy(ext, "EXT\0\0", 5);
-        function = context->getProcAddress(fn);
-    }
+        if (!function && (policy & ResolveEXT)) {
+            memcpy(ext, "EXT", 4);
+            function = context->getProcAddress(fn);
+        }
 
-    if (!function && (policy & ResolveANGLE)) {
-        memcpy(ext, "ANGLE", 5);
-        function = context->getProcAddress(fn);
-    }
+        if (!function && (policy & ResolveANGLE)) {
+            memcpy(ext, "ANGLE", 6);
+            function = context->getProcAddress(fn);
+        }
 
-    if (!function && (policy & ResolveNV)) {
-        memcpy(ext, "NV\0\0\0", 5);
-        function = context->getProcAddress(fn);
+        if (!function && (policy & ResolveNV)) {
+            memcpy(ext, "NV", 3);
+            function = context->getProcAddress(fn);
+        }
     }
 
     return function;