From 8a178ebe55507112c834ac3d7edb4626c9a8cfc1 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Tue, 9 Jun 2020 21:59:25 +0530
Subject: [PATCH] Wayland: Apply the same framebuffer selection optimisation

Not as much of a win, since EGL only causes approx 1K getpid() calls of
which this optimization eliminates only half
---
 glfw/context.c     | 168 ---------------------------------------------
 glfw/egl_context.c |  98 ++++++++++----------------
 glfw/egl_context.h |   3 +
 glfw/internal.h    |   3 -
 4 files changed, 38 insertions(+), 234 deletions(-)

diff --git a/glfw/context.c b/glfw/context.c
index dec0b141d..b2d9199af 100644
--- a/glfw/context.c
+++ b/glfw/context.c
@@ -173,174 +173,6 @@ bool _glfwIsValidContextConfig(const _GLFWctxconfig* ctxconfig)
     return true;
 }
 
-// Chooses the framebuffer config that best matches the desired one
-//
-const _GLFWfbconfig* _glfwChooseFBConfig(const _GLFWfbconfig* desired,
-                                         const _GLFWfbconfig* alternatives,
-                                         unsigned int count)
-{
-    unsigned int i;
-    unsigned int missing, leastMissing = UINT_MAX;
-    unsigned int colorDiff, leastColorDiff = UINT_MAX;
-    unsigned int extraDiff, leastExtraDiff = UINT_MAX;
-    const _GLFWfbconfig* current;
-    const _GLFWfbconfig* closest = NULL;
-
-    for (i = 0;  i < count;  i++)
-    {
-        current = alternatives + i;
-
-        if (desired->stereo > 0 && current->stereo == 0)
-        {
-            // Stereo is a hard constraint
-            continue;
-        }
-
-        if (desired->doublebuffer != current->doublebuffer)
-        {
-            // Double buffering is a hard constraint
-            continue;
-        }
-
-        // Count number of missing buffers
-        {
-            missing = 0;
-
-            if (desired->alphaBits > 0 && current->alphaBits == 0)
-                missing++;
-
-            if (desired->depthBits > 0 && current->depthBits == 0)
-                missing++;
-
-            if (desired->stencilBits > 0 && current->stencilBits == 0)
-                missing++;
-
-            if (desired->auxBuffers > 0 &&
-                current->auxBuffers < desired->auxBuffers)
-            {
-                missing += desired->auxBuffers - current->auxBuffers;
-            }
-
-            if (desired->samples > 0 && current->samples == 0)
-            {
-                // Technically, several multisampling buffers could be
-                // involved, but that's a lower level implementation detail and
-                // not important to us here, so we count them as one
-                missing++;
-            }
-
-            if (desired->transparent != current->transparent)
-                missing++;
-        }
-
-        // These polynomials make many small channel size differences matter
-        // less than one large channel size difference
-
-        // Calculate color channel size difference value
-        {
-            colorDiff = 0;
-
-            if (desired->redBits != GLFW_DONT_CARE)
-            {
-                colorDiff += (desired->redBits - current->redBits) *
-                             (desired->redBits - current->redBits);
-            }
-
-            if (desired->greenBits != GLFW_DONT_CARE)
-            {
-                colorDiff += (desired->greenBits - current->greenBits) *
-                             (desired->greenBits - current->greenBits);
-            }
-
-            if (desired->blueBits != GLFW_DONT_CARE)
-            {
-                colorDiff += (desired->blueBits - current->blueBits) *
-                             (desired->blueBits - current->blueBits);
-            }
-        }
-
-        // Calculate non-color channel size difference value
-        {
-            extraDiff = 0;
-
-            if (desired->alphaBits != GLFW_DONT_CARE)
-            {
-                extraDiff += (desired->alphaBits - current->alphaBits) *
-                             (desired->alphaBits - current->alphaBits);
-            }
-
-            if (desired->depthBits != GLFW_DONT_CARE)
-            {
-                extraDiff += (desired->depthBits - current->depthBits) *
-                             (desired->depthBits - current->depthBits);
-            }
-
-            if (desired->stencilBits != GLFW_DONT_CARE)
-            {
-                extraDiff += (desired->stencilBits - current->stencilBits) *
-                             (desired->stencilBits - current->stencilBits);
-            }
-
-            if (desired->accumRedBits != GLFW_DONT_CARE)
-            {
-                extraDiff += (desired->accumRedBits - current->accumRedBits) *
-                             (desired->accumRedBits - current->accumRedBits);
-            }
-
-            if (desired->accumGreenBits != GLFW_DONT_CARE)
-            {
-                extraDiff += (desired->accumGreenBits - current->accumGreenBits) *
-                             (desired->accumGreenBits - current->accumGreenBits);
-            }
-
-            if (desired->accumBlueBits != GLFW_DONT_CARE)
-            {
-                extraDiff += (desired->accumBlueBits - current->accumBlueBits) *
-                             (desired->accumBlueBits - current->accumBlueBits);
-            }
-
-            if (desired->accumAlphaBits != GLFW_DONT_CARE)
-            {
-                extraDiff += (desired->accumAlphaBits - current->accumAlphaBits) *
-                             (desired->accumAlphaBits - current->accumAlphaBits);
-            }
-
-            if (desired->samples != GLFW_DONT_CARE)
-            {
-                extraDiff += (desired->samples - current->samples) *
-                             (desired->samples - current->samples);
-            }
-
-            if (desired->sRGB && !current->sRGB)
-                extraDiff++;
-        }
-
-        // Figure out if the current one is better than the best one found so far
-        // Least number of missing buffers is the most important heuristic,
-        // then color buffer size match and lastly size match for other buffers
-
-        if (missing < leastMissing)
-            closest = current;
-        else if (missing == leastMissing)
-        {
-            if ((colorDiff < leastColorDiff) ||
-                (colorDiff == leastColorDiff && extraDiff < leastExtraDiff))
-            {
-                closest = current;
-            }
-        }
-
-        if (current == closest)
-        {
-            leastMissing = missing;
-            leastColorDiff = colorDiff;
-            leastExtraDiff = extraDiff;
-        }
-    }
-
-    return closest;
-}
-
 // Retrieves the attributes of the current context
 //
 bool _glfwRefreshContextAttribs(_GLFWwindow* window,
diff --git a/glfw/egl_context.c b/glfw/egl_context.c
index 39786760a..82333db5c 100644
--- a/glfw/egl_context.c
+++ b/glfw/egl_context.c
@@ -76,6 +76,7 @@ static const char* getEGLErrorString(EGLint error)
     }
 }
 
+#ifdef _GLFW_X11
 // Returns the specified attribute of the specified EGLConfig
 //
 static int getEGLConfigAttrib(EGLConfig config, int attrib)
@@ -84,6 +85,7 @@ static int getEGLConfigAttrib(EGLConfig config, int attrib)
     eglGetConfigAttrib(_glfw.egl.display, config, attrib, &value);
     return value;
 }
+#endif
 
 // Return the EGLConfig most closely matching the specified hints
 //
@@ -91,39 +93,44 @@ static bool chooseEGLConfig(const _GLFWctxconfig* ctxconfig,
                                 const _GLFWfbconfig* desired,
                                 EGLConfig* result)
 {
-    EGLConfig* nativeConfigs;
-    _GLFWfbconfig* usableConfigs;
-    const _GLFWfbconfig* closest;
-    int i, nativeCount, usableCount;
+    EGLConfig configs[512];
+    int i = 0, nativeCount = 0, ans_idx = 0;
+    EGLint attributes[64];
+#define ATTR(k, v) { attributes[i++] = k; attributes[i++] = v; }
+    ATTR(EGL_COLOR_BUFFER_TYPE, EGL_RGB_BUFFER);
+    ATTR(EGL_SURFACE_TYPE, EGL_WINDOW_BIT);
+    if (ctxconfig->client == GLFW_OPENGL_ES_API) {
+        if (ctxconfig->major == 1) ATTR(EGL_RENDERABLE_TYPE, EGL_OPENGL_ES_BIT)
+        else ATTR(EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT);
+    }
+    else if (ctxconfig->client == GLFW_OPENGL_API) ATTR(EGL_RENDERABLE_TYPE, EGL_OPENGL_BIT);
+    if (desired->samples > 0) ATTR(EGL_SAMPLES, desired->samples);
+    if (desired->depthBits > 0) ATTR(EGL_DEPTH_SIZE, desired->depthBits);
+    if (desired->stencilBits > 0) ATTR(EGL_STENCIL_SIZE, desired->stencilBits);
+    if (desired->redBits > 0) ATTR(EGL_RED_SIZE, desired->redBits);
+    if (desired->greenBits > 0) ATTR(EGL_GREEN_SIZE, desired->greenBits);
+    if (desired->blueBits > 0) ATTR(EGL_BLUE_SIZE, desired->blueBits);
+    if (desired->alphaBits > 0) ATTR(EGL_ALPHA_SIZE, desired->alphaBits);
+    ATTR(EGL_NONE, EGL_NONE);
+#undef ATTR
+    if (!eglChooseConfig(_glfw.egl.display, attributes, configs, sizeof(configs)/sizeof(configs[0]), &nativeCount)) {
+        _glfwInputError(GLFW_API_UNAVAILABLE, "EGL: eglChooseConfig failed");
+        return false;
+    }
 
-    eglGetConfigs(_glfw.egl.display, NULL, 0, &nativeCount);
     if (!nativeCount)
     {
         _glfwInputError(GLFW_API_UNAVAILABLE, "EGL: No EGLConfigs returned");
         return false;
     }
 
-    nativeConfigs = calloc(nativeCount, sizeof(EGLConfig));
-    eglGetConfigs(_glfw.egl.display, nativeConfigs, nativeCount, &nativeCount);
-
-    usableConfigs = calloc(nativeCount, sizeof(_GLFWfbconfig));
-    usableCount = 0;
 
     for (i = 0;  i < nativeCount;  i++)
     {
-        const EGLConfig n = nativeConfigs[i];
-        _GLFWfbconfig* u = usableConfigs + usableCount;
-
-        // Only consider RGB(A) EGLConfigs
-        if (getEGLConfigAttrib(n, EGL_COLOR_BUFFER_TYPE) != EGL_RGB_BUFFER)
-            continue;
-
-        // Only consider window EGLConfigs
-        if (!(getEGLConfigAttrib(n, EGL_SURFACE_TYPE) & EGL_WINDOW_BIT))
-            continue;
 
 #if defined(_GLFW_X11)
         {
+            const EGLConfig n = configs[i];
             XVisualInfo vi = {0};
 
             // Only consider EGLConfigs with associated Visuals
@@ -138,55 +145,18 @@ static bool chooseEGLConfig(const _GLFWctxconfig* ctxconfig,
                     XGetVisualInfo(_glfw.x11.display, VisualIDMask, &vi, &count);
                 if (vis)
                 {
-                    u->transparent = _glfwIsVisualTransparentX11(vis[0].visual);
+                    bool transparent = _glfwIsVisualTransparentX11(vis[0].visual);
                     XFree(vis);
+                    if (!transparent) continue;
                 }
             }
         }
 #endif // _GLFW_X11
-
-        if (ctxconfig->client == GLFW_OPENGL_ES_API)
-        {
-            if (ctxconfig->major == 1)
-            {
-                if (!(getEGLConfigAttrib(n, EGL_RENDERABLE_TYPE) & EGL_OPENGL_ES_BIT))
-                    continue;
-            }
-            else
-            {
-                if (!(getEGLConfigAttrib(n, EGL_RENDERABLE_TYPE) & EGL_OPENGL_ES2_BIT))
-                    continue;
-            }
-        }
-        else if (ctxconfig->client == GLFW_OPENGL_API)
-        {
-            if (!(getEGLConfigAttrib(n, EGL_RENDERABLE_TYPE) & EGL_OPENGL_BIT))
-                continue;
-        }
-
-        u->redBits = getEGLConfigAttrib(n, EGL_RED_SIZE);
-        u->greenBits = getEGLConfigAttrib(n, EGL_GREEN_SIZE);
-        u->blueBits = getEGLConfigAttrib(n, EGL_BLUE_SIZE);
-
-        u->alphaBits = getEGLConfigAttrib(n, EGL_ALPHA_SIZE);
-        u->depthBits = getEGLConfigAttrib(n, EGL_DEPTH_SIZE);
-        u->stencilBits = getEGLConfigAttrib(n, EGL_STENCIL_SIZE);
-
-        u->samples = getEGLConfigAttrib(n, EGL_SAMPLES);
-        u->doublebuffer = true;
-
-        u->handle = (uintptr_t) n;
-        usableCount++;
+        ans_idx = i;
+        break;
     }
-
-    closest = _glfwChooseFBConfig(desired, usableConfigs, usableCount);
-    if (closest)
-        *result = (EGLConfig) closest->handle;
-
-    free(nativeConfigs);
-    free(usableConfigs);
-
-    return closest != NULL;
+    *result = configs[ans_idx];
+    return true;
 }
 
 static void makeContextCurrentEGL(_GLFWwindow* window)
@@ -340,6 +310,7 @@ bool _glfwInitEGL(void)
 
     glfw_dlsym(_glfw.egl.GetConfigAttrib, _glfw.egl.handle, "eglGetConfigAttrib");
     glfw_dlsym(_glfw.egl.GetConfigs, _glfw.egl.handle, "eglGetConfigs");
+    glfw_dlsym(_glfw.egl.ChooseConfig, _glfw.egl.handle, "eglChooseConfig");
     glfw_dlsym(_glfw.egl.GetDisplay, _glfw.egl.handle, "eglGetDisplay");
     glfw_dlsym(_glfw.egl.GetError, _glfw.egl.handle, "eglGetError");
     glfw_dlsym(_glfw.egl.Initialize, _glfw.egl.handle, "eglInitialize");
@@ -357,6 +328,7 @@ bool _glfwInitEGL(void)
 
     if (!_glfw.egl.GetConfigAttrib ||
         !_glfw.egl.GetConfigs ||
+        !_glfw.egl.ChooseConfig ||
         !_glfw.egl.GetDisplay ||
         !_glfw.egl.GetError ||
         !_glfw.egl.Initialize ||
diff --git a/glfw/egl_context.h b/glfw/egl_context.h
index baae5d160..362de2fe0 100644
--- a/glfw/egl_context.h
+++ b/glfw/egl_context.h
@@ -120,6 +120,7 @@ typedef void* EGLSurface;
 // EGL function pointer typedefs
 typedef EGLBoolean (EGLAPIENTRY * PFN_eglGetConfigAttrib)(EGLDisplay,EGLConfig,EGLint,EGLint*);
 typedef EGLBoolean (EGLAPIENTRY * PFN_eglGetConfigs)(EGLDisplay,EGLConfig*,EGLint,EGLint*);
+typedef EGLBoolean (EGLAPIENTRY * PFN_eglChooseConfig)(EGLDisplay,EGLint const*,EGLConfig*,EGLint,EGLint*);
 typedef EGLDisplay (EGLAPIENTRY * PFN_eglGetDisplay)(EGLNativeDisplayType);
 typedef EGLint (EGLAPIENTRY * PFN_eglGetError)(void);
 typedef EGLBoolean (EGLAPIENTRY * PFN_eglInitialize)(EGLDisplay,EGLint*,EGLint*);
@@ -136,6 +137,7 @@ typedef const char* (EGLAPIENTRY * PFN_eglQueryString)(EGLDisplay,EGLint);
 typedef GLFWglproc (EGLAPIENTRY * PFN_eglGetProcAddress)(const char*);
 #define eglGetConfigAttrib _glfw.egl.GetConfigAttrib
 #define eglGetConfigs _glfw.egl.GetConfigs
+#define eglChooseConfig _glfw.egl.ChooseConfig
 #define eglGetDisplay _glfw.egl.GetDisplay
 #define eglGetError _glfw.egl.GetError
 #define eglInitialize _glfw.egl.Initialize
@@ -185,6 +187,7 @@ typedef struct _GLFWlibraryEGL
 
     PFN_eglGetConfigAttrib      GetConfigAttrib;
     PFN_eglGetConfigs           GetConfigs;
+    PFN_eglChooseConfig         ChooseConfig;
     PFN_eglGetDisplay           GetDisplay;
     PFN_eglGetError             GetError;
     PFN_eglInitialize           Initialize;
diff --git a/glfw/internal.h b/glfw/internal.h
index 98d08fad1..b6ff86f62 100644
--- a/glfw/internal.h
+++ b/glfw/internal.h
@@ -794,9 +794,6 @@ void _glfwDebug(const char* format, ...);
 //////////////////////////////////////////////////////////////////////////
 
 bool _glfwStringInExtensionString(const char* string, const char* extensions);
-const _GLFWfbconfig* _glfwChooseFBConfig(const _GLFWfbconfig* desired,
-                                         const _GLFWfbconfig* alternatives,
-                                         unsigned int count);
 bool _glfwRefreshContextAttribs(_GLFWwindow* window,
                                     const _GLFWctxconfig* ctxconfig);
 bool _glfwIsValidContextConfig(const _GLFWctxconfig* ctxconfig);