Cache WGL extension function pointers

These took about 20 ms to look up, and we were doing so at least twice per
sink. On my desktop windows machine, this saves 25 seconds when running

  dm --config gl --src gm

Actual times dropped from 63s to 37s if not writing PNGs,
or 71s to 46s if writing PNGs.

Bug: skia:
Change-Id: I22313791939e774290b702e58fec780f0b9c917e
Reviewed-on: https://skia-review.googlesource.com/35422
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

2 files changed, 70 insertions, 62 deletions

diff --git a/src/utils/win/SkWGL.h b/src/utils/win/SkWGL.h
index 1fafd2fe52..315be24cd9 100644
--- a/src/utils/win/SkWGL.h
+++ b/src/utils/win/SkWGL.h
@@ -105,16 +105,16 @@ private:
     typedef int (WINAPI* ReleasePbufferDCProc)(HPBUFFER, HDC);
     typedef BOOL (WINAPI* DestroyPbufferProc)(HPBUFFER);
 
-    GetExtensionsStringProc fGetExtensionsString;
-    ChoosePixelFormatProc fChoosePixelFormat;
-    GetPixelFormatAttribfvProc fGetPixelFormatAttribfv;
-    GetPixelFormatAttribivProc fGetPixelFormatAttribiv;
-    CreateContextAttribsProc fCreateContextAttribs;
-    SwapIntervalProc fSwapInterval;
-    CreatePbufferProc fCreatePbuffer;
-    GetPbufferDCProc fGetPbufferDC;
-    ReleasePbufferDCProc fReleasePbufferDC;
-    DestroyPbufferProc fDestroyPbuffer;
+    static GetExtensionsStringProc fGetExtensionsString;
+    static ChoosePixelFormatProc fChoosePixelFormat;
+    static GetPixelFormatAttribfvProc fGetPixelFormatAttribfv;
+    static GetPixelFormatAttribivProc fGetPixelFormatAttribiv;
+    static CreateContextAttribsProc fCreateContextAttribs;
+    static SwapIntervalProc fSwapInterval;
+    static CreatePbufferProc fCreatePbuffer;
+    static GetPbufferDCProc fGetPbufferDC;
+    static ReleasePbufferDCProc fReleasePbufferDC;
+    static DestroyPbufferProc fDestroyPbuffer;
 };
 
 enum SkWGLContextRequest {
diff --git a/src/utils/win/SkWGL_win.cpp b/src/utils/win/SkWGL_win.cpp
index cce7a56b75..cc95f4988d 100644
--- a/src/utils/win/SkWGL_win.cpp
+++ b/src/utils/win/SkWGL_win.cpp
@@ -10,6 +10,7 @@
 
 #include "SkWGL.h"
 
+#include "SkOnce.h"
 #include "SkTDArray.h"
 #include "SkTSearch.h"
 #include "SkTSort.h"
@@ -231,58 +232,65 @@ void destroy_dummy_window(HWND dummy) {
 #define GET_PROC(NAME, SUFFIX) f##NAME = \
                      (NAME##Proc) wglGetProcAddress("wgl" #NAME #SUFFIX)
 
-SkWGLExtensions::SkWGLExtensions()
-    : fGetExtensionsString(nullptr)
-    , fChoosePixelFormat(nullptr)
-    , fGetPixelFormatAttribfv(nullptr)
-    , fGetPixelFormatAttribiv(nullptr)
-    , fCreateContextAttribs(nullptr)
-    , fSwapInterval(nullptr)
-    , fCreatePbuffer(nullptr)
-    , fGetPbufferDC(nullptr)
-    , fReleasePbufferDC(nullptr)
-    , fDestroyPbuffer(nullptr)
- {
-    HDC prevDC = wglGetCurrentDC();
-    HGLRC prevGLRC = wglGetCurrentContext();
 
-    PIXELFORMATDESCRIPTOR dummyPFD;
-
-    ZeroMemory(&dummyPFD, sizeof(dummyPFD));
-    dummyPFD.nSize = sizeof(dummyPFD);
-    dummyPFD.nVersion = 1;
-    dummyPFD.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL;
-    dummyPFD.iPixelType = PFD_TYPE_RGBA;
-    dummyPFD.cColorBits  = 32;
-    dummyPFD.cDepthBits  = 0;
-    dummyPFD.cStencilBits = 8;
-    dummyPFD.iLayerType = PFD_MAIN_PLANE;
-    HWND dummyWND = create_dummy_window();
-    if (dummyWND) {
-        HDC dummyDC = GetDC(dummyWND);
-        int dummyFormat = ChoosePixelFormat(dummyDC, &dummyPFD);
-        SetPixelFormat(dummyDC, dummyFormat, &dummyPFD);
-        HGLRC dummyGLRC = wglCreateContext(dummyDC);
-        SkASSERT(dummyGLRC);
-        wglMakeCurrent(dummyDC, dummyGLRC);
-
-        GET_PROC(GetExtensionsString, ARB);
-        GET_PROC(ChoosePixelFormat, ARB);
-        GET_PROC(GetPixelFormatAttribiv, ARB);
-        GET_PROC(GetPixelFormatAttribfv, ARB);
-        GET_PROC(CreateContextAttribs, ARB);
-        GET_PROC(SwapInterval, EXT);
-        GET_PROC(CreatePbuffer, ARB);
-        GET_PROC(GetPbufferDC, ARB);
-        GET_PROC(ReleasePbufferDC, ARB);
-        GET_PROC(DestroyPbuffer, ARB);
-
-        wglMakeCurrent(dummyDC, nullptr);
-        wglDeleteContext(dummyGLRC);
-        destroy_dummy_window(dummyWND);
-    }
+SkWGLExtensions::GetExtensionsStringProc SkWGLExtensions::fGetExtensionsString = nullptr;
+SkWGLExtensions::ChoosePixelFormatProc SkWGLExtensions::fChoosePixelFormat = nullptr;
+SkWGLExtensions::GetPixelFormatAttribfvProc SkWGLExtensions::fGetPixelFormatAttribfv = nullptr;
+SkWGLExtensions::GetPixelFormatAttribivProc SkWGLExtensions::fGetPixelFormatAttribiv = nullptr;
+SkWGLExtensions::CreateContextAttribsProc SkWGLExtensions::fCreateContextAttribs = nullptr;
+SkWGLExtensions::SwapIntervalProc SkWGLExtensions::fSwapInterval = nullptr;
+SkWGLExtensions::CreatePbufferProc SkWGLExtensions::fCreatePbuffer = nullptr;
+SkWGLExtensions::GetPbufferDCProc SkWGLExtensions::fGetPbufferDC = nullptr;
+SkWGLExtensions::ReleasePbufferDCProc SkWGLExtensions::fReleasePbufferDC = nullptr;
+SkWGLExtensions::DestroyPbufferProc SkWGLExtensions::fDestroyPbuffer = nullptr;
+
+SkWGLExtensions::SkWGLExtensions() {
+    // We cache these function pointers once, and then reuse them. That's possibly incorrect if
+    // there are multiple GPUs, or if we intend to use these for rendering contexts of different
+    // pixel formats (where wglGetProcAddress is not guaranteed to return the same pointer).
+    static SkOnce once;
+    once([] {
+        HDC prevDC = wglGetCurrentDC();
+        HGLRC prevGLRC = wglGetCurrentContext();
+
+        PIXELFORMATDESCRIPTOR dummyPFD;
+
+        ZeroMemory(&dummyPFD, sizeof(dummyPFD));
+        dummyPFD.nSize = sizeof(dummyPFD);
+        dummyPFD.nVersion = 1;
+        dummyPFD.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL;
+        dummyPFD.iPixelType = PFD_TYPE_RGBA;
+        dummyPFD.cColorBits  = 32;
+        dummyPFD.cDepthBits  = 0;
+        dummyPFD.cStencilBits = 8;
+        dummyPFD.iLayerType = PFD_MAIN_PLANE;
+        HWND dummyWND = create_dummy_window();
+        if (dummyWND) {
+            HDC dummyDC = GetDC(dummyWND);
+            int dummyFormat = ChoosePixelFormat(dummyDC, &dummyPFD);
+            SetPixelFormat(dummyDC, dummyFormat, &dummyPFD);
+            HGLRC dummyGLRC = wglCreateContext(dummyDC);
+            SkASSERT(dummyGLRC);
+            wglMakeCurrent(dummyDC, dummyGLRC);
+
+            GET_PROC(GetExtensionsString, ARB);
+            GET_PROC(ChoosePixelFormat, ARB);
+            GET_PROC(GetPixelFormatAttribiv, ARB);
+            GET_PROC(GetPixelFormatAttribfv, ARB);
+            GET_PROC(CreateContextAttribs, ARB);
+            GET_PROC(SwapInterval, EXT);
+            GET_PROC(CreatePbuffer, ARB);
+            GET_PROC(GetPbufferDC, ARB);
+            GET_PROC(ReleasePbufferDC, ARB);
+            GET_PROC(DestroyPbuffer, ARB);
+
+            wglMakeCurrent(dummyDC, nullptr);
+            wglDeleteContext(dummyGLRC);
+            destroy_dummy_window(dummyWND);
+        }
 
-    wglMakeCurrent(prevDC, prevGLRC);
+        wglMakeCurrent(prevDC, prevGLRC);
+    });
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -334,8 +342,8 @@ static void get_pixel_formats_to_try(HDC dc, const SkWGLExtensions& extensions,
     extensions.choosePixelFormat(dc, iAttrs.begin(), fAttrs, 1, format, &num);
 }
 
-static HGLRC create_gl_context(HDC dc, SkWGLExtensions extensions, SkWGLContextRequest contextType,
-                               HGLRC shareContext) {
+static HGLRC create_gl_context(HDC dc, const SkWGLExtensions& extensions,
+                               SkWGLContextRequest contextType, HGLRC shareContext) {
     HDC prevDC = wglGetCurrentDC();
     HGLRC prevGLRC = wglGetCurrentContext();