Unify wgl context creation.

R=robertphillips@google.com
Review URL: https://codereview.chromium.org/12455009

git-svn-id: http://skia.googlecode.com/svn/trunk@7990 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 106 insertions, 0 deletions

diff --git a/src/utils/win/SkWGL_win.cpp b/src/utils/win/SkWGL_win.cpp
index 48b270d079..35153f2093 100644
--- a/src/utils/win/SkWGL_win.cpp
+++ b/src/utils/win/SkWGL_win.cpp
@@ -263,3 +263,109 @@ SkWGLExtensions::SkWGLExtensions()
 
     wglMakeCurrent(prevDC, prevGLRC);
 }
+
+HGLRC SkCreateWGLContext(HDC dc, int msaaSampleCount, bool preferCoreProfile) {
+    SkWGLExtensions extensions;
+    if (!extensions.hasExtension(dc, "WGL_ARB_pixel_format")) {
+        return NULL;
+    }
+
+    HDC prevDC = wglGetCurrentDC();
+    HGLRC prevGLRC = wglGetCurrentContext();
+    PIXELFORMATDESCRIPTOR pfd;
+
+    int format = 0;
+
+    static const int iAttrs[] = {
+        SK_WGL_DRAW_TO_WINDOW, TRUE,
+        SK_WGL_DOUBLE_BUFFER, TRUE,
+        SK_WGL_ACCELERATION, SK_WGL_FULL_ACCELERATION,
+        SK_WGL_SUPPORT_OPENGL, TRUE,
+        SK_WGL_COLOR_BITS, 24,
+        SK_WGL_ALPHA_BITS, 8,
+        SK_WGL_STENCIL_BITS, 8,
+        0, 0
+    };
+
+    float fAttrs[] = {0, 0};
+
+    if (msaaSampleCount > 0 &&
+        extensions.hasExtension(dc, "WGL_ARB_multisample")) {
+        static const int kIAttrsCount = SK_ARRAY_COUNT(iAttrs);
+        int msaaIAttrs[kIAttrsCount + 6];
+        memcpy(msaaIAttrs, iAttrs, sizeof(int) * kIAttrsCount);
+        SkASSERT(0 == msaaIAttrs[kIAttrsCount - 2] &&
+                 0 == msaaIAttrs[kIAttrsCount - 1]);
+        msaaIAttrs[kIAttrsCount - 2] = SK_WGL_SAMPLE_BUFFERS;
+        msaaIAttrs[kIAttrsCount - 1] = TRUE;
+        msaaIAttrs[kIAttrsCount + 0] = SK_WGL_SAMPLES;
+        msaaIAttrs[kIAttrsCount + 1] = msaaSampleCount;
+        if (extensions.hasExtension(dc, "WGL_NV_multisample_coverage")) {
+            msaaIAttrs[kIAttrsCount + 2] = SK_WGL_COLOR_SAMPLES;
+            // We want the fewest number of color samples possible.
+            // Passing 0 gives only the formats where all samples are color
+            // samples.
+            msaaIAttrs[kIAttrsCount + 3] = 1;
+            msaaIAttrs[kIAttrsCount + 4] = 0;
+            msaaIAttrs[kIAttrsCount + 5] = 0;
+        } else {
+            msaaIAttrs[kIAttrsCount + 2] = 0;
+            msaaIAttrs[kIAttrsCount + 3] = 0;
+        }
+        unsigned int num;
+        int formats[64];
+        extensions.choosePixelFormat(dc, msaaIAttrs, fAttrs, 64, formats, &num);
+        num = min(num,64);
+        int formatToTry = extensions.selectFormat(formats,
+                                                  num,
+                                                  dc,
+                                                  msaaSampleCount);
+        DescribePixelFormat(dc, formatToTry, sizeof(pfd), &pfd);
+        if (SetPixelFormat(dc, formatToTry, &pfd)) {
+            format = formatToTry;
+        }
+    }
+
+    if (0 == format) {
+        // Either MSAA wasn't requested or creation failed
+        unsigned int num;
+        extensions.choosePixelFormat(dc, iAttrs, fAttrs, 1, &format, &num);
+        DescribePixelFormat(dc, format, sizeof(pfd), &pfd);
+        BOOL set = SetPixelFormat(dc, format, &pfd);
+        SkASSERT(TRUE == set);
+    }
+
+    HGLRC glrc = NULL;
+    if (preferCoreProfile && extensions.hasExtension(dc, "WGL_ARB_create_context")) {
+        static const int kCoreGLVersions[] = {
+            4, 3,
+            4, 2,
+            4, 1,
+            4, 0,
+            3, 3,
+            3, 2,
+        };
+        int coreProfileAttribs[] = {
+            SK_WGL_CONTEXT_MAJOR_VERSION, -1,
+            SK_WGL_CONTEXT_MINOR_VERSION, -1,
+            SK_WGL_CONTEXT_PROFILE_MASK,  SK_WGL_CONTEXT_CORE_PROFILE_BIT,
+            0,
+        };
+        for (int v = 0; v < SK_ARRAY_COUNT(kCoreGLVersions) / 2; ++v) {
+            coreProfileAttribs[1] = kCoreGLVersions[2 * v];
+            coreProfileAttribs[3] = kCoreGLVersions[2 * v + 1];
+            glrc = extensions.createContextAttribs(dc, NULL, coreProfileAttribs);
+            if (NULL != glrc) {
+                break;
+            }
+        }
+    }
+
+    if (NULL == glrc) {
+        glrc = wglCreateContext(dc);
+    }
+    SkASSERT(glrc);
+
+    wglMakeCurrent(prevDC, prevGLRC);
+    return glrc;
+}