Add headless OSMesa backend

Allows creation and drawing to in-memory OpenGL contexts. This backend does not provide input. Related to #850.
2026-09-20 16:30:45 +00:00 · 2016-08-30 15:53:19 -07:00
parent a90ee65f7b
commit 368fa9475d
12 changed files with 766 additions and 0 deletions
@@ -0,0 +1,213 @@
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "internal.h"
+#include "osmesa_context.h"
+
+static void makeContextCurrentOSMesa(_GLFWwindow* window)
+{
+    if (window)
+    {
+        // Check to see if we need to allocate a new buffer.
+        if ((window->context.osmesa.buffer == NULL) ||
+            (window->osmesa.width != window->context.osmesa.width) ||
+            (window->osmesa.height != window->context.osmesa.height))
+        {
+            // Free the current buffer, if necessary.
+            if (window->context.osmesa.buffer != NULL)
+            {
+                free(window->context.osmesa.buffer);
+            }
+
+            // Allocate the new buffer (width * height * 1 byte per RGBA
+            // channel).
+            window->context.osmesa.buffer = (unsigned char *) malloc(
+                window->osmesa.width * window->osmesa.height * 4);
+
+            // Update the context size.
+            window->context.osmesa.width = window->osmesa.width;
+            window->context.osmesa.height = window->osmesa.height;
+        }
+
+        // Make the context current.
+        if (!OSMesaMakeCurrent(window->context.osmesa.handle,
+                            window->context.osmesa.buffer,
+                            0x1401, // GL_UNSIGNED_BYTE
+                            window->osmesa.width, window->osmesa.height))
+        {
+            _glfwInputError(GLFW_PLATFORM_ERROR,
+                            "OSMesa: Failed to make context current.");
+            return;
+        }
+    }
+    else
+    {
+        _glfwInputError(GLFW_PLATFORM_ERROR,
+            "OSMesa: Releasing the current context is not supported.");
+    }
+
+    _glfwPlatformSetCurrentContext(window);
+}
+
+static GLFWglproc getProcAddressOSMesa(const char* procname)
+{
+    _GLFWwindow* window = _glfwPlatformGetCurrentContext();
+
+    if (window->context.osmesa.handle)
+    {
+        return (GLFWglproc) OSMesaGetProcAddress(procname);
+    }
+
+    return NULL;
+}
+
+static void destroyContextOSMesa(_GLFWwindow* window)
+{
+    if (window->context.osmesa.handle != NULL)
+    {
+        OSMesaDestroyContext(window->context.osmesa.handle);
+        window->context.osmesa.handle = NULL;
+    }
+
+    if (window->context.osmesa.buffer != NULL)
+    {
+        free(window->context.osmesa.buffer);
+        window->context.osmesa.width = 0;
+        window->context.osmesa.height = 0;
+    }
+}
+
+static void swapBuffersOSMesa(_GLFWwindow* window) {}
+
+static void swapIntervalOSMesa(int interval) {}
+
+static int extensionSupportedOSMesa()
+{
+    return GLFW_FALSE;
+}
+
+//////////////////////////////////////////////////////////////////////////
+//////                       GLFW internal API                      //////
+//////////////////////////////////////////////////////////////////////////
+
+GLFWbool _glfwInitOSMesa(void)
+{
+    int i;
+    const char* sonames[] =
+    {
+#if defined(_GLFW_WIN32)
+        "libOSMesa.dll",
+        "OSMesa.dll",
+#elif defined(_GLFW_COCOA)
+        "libOSMesa.dylib",
+#else
+        "libOSMesa.so.6",
+#endif
+        NULL
+    };
+
+    if (_glfw.osmesa.handle)
+        return GLFW_TRUE;
+
+    for (i = 0;  sonames[i];  i++)
+    {
+        _glfw.osmesa.handle = _glfw_dlopen(sonames[i]);
+        if (_glfw.osmesa.handle)
+            break;
+    }
+
+    if (!_glfw.osmesa.handle)
+    {
+        _glfwInputError(GLFW_API_UNAVAILABLE, "OSMesa: Library not found");
+        return GLFW_FALSE;
+    }
+
+    _glfw.osmesa.prefix = (strncmp(sonames[i], "lib", 3) == 0);
+
+    _glfw.osmesa.CreateContext = (PFNOSMESACREATECONTEXTPROC)
+        _glfw_dlsym(_glfw.osmesa.handle, "OSMesaCreateContext");
+    _glfw.osmesa.DestroyContext = (PFNOSMESADESTROYCONTEXTPROC)
+        _glfw_dlsym(_glfw.osmesa.handle, "OSMesaDestroyContext");
+    _glfw.osmesa.MakeCurrent = (PFNOSMESAMAKECURRENTPROC)
+        _glfw_dlsym(_glfw.osmesa.handle, "OSMesaMakeCurrent");
+    _glfw.osmesa.GetCurrentContext = (PFNOSMESAGETCURRENTCONTEXTPROC)
+        _glfw_dlsym(_glfw.osmesa.handle, "OSMesaGetCurrentContext");
+    _glfw.osmesa.PixelStore = (PFNOSMESAPIXELSTOREPROC)
+        _glfw_dlsym(_glfw.osmesa.handle, "OSMesaPixelStore");
+    _glfw.osmesa.GetIntegerv = (PFNOSMESAGETINTEGERVPROC)
+        _glfw_dlsym(_glfw.osmesa.handle, "OSMesaGetIntegerv");
+    _glfw.osmesa.GetColorBuffer = (PFNOSMESAGETCOLORBUFFERPROC)
+        _glfw_dlsym(_glfw.osmesa.handle, "OSMesaGetColorBuffer");
+    _glfw.osmesa.GetDepthBuffer = (PFNOSMESAGETDEPTHBUFFERPROC)
+        _glfw_dlsym(_glfw.osmesa.handle, "OSMesaGetDepthBuffer");
+    _glfw.osmesa.GetProcAddress = (PFNOSMESAGETPROCADDRESSPROC)
+        _glfw_dlsym(_glfw.osmesa.handle, "OSMesaGetProcAddress");
+
+    if (!_glfw.osmesa.CreateContext ||
+        !_glfw.osmesa.DestroyContext ||
+        !_glfw.osmesa.MakeCurrent ||
+        !_glfw.osmesa.GetCurrentContext ||
+        !_glfw.osmesa.PixelStore ||
+        !_glfw.osmesa.GetIntegerv ||
+        !_glfw.osmesa.GetColorBuffer ||
+        !_glfw.osmesa.GetDepthBuffer ||
+        !_glfw.osmesa.GetProcAddress)
+    {
+        _glfwInputError(GLFW_PLATFORM_ERROR,
+                        "OSMesa: Failed to load required entry points");
+
+        _glfwTerminateOSMesa();
+        return GLFW_FALSE;
+    }
+
+    return GLFW_TRUE;
+}
+
+void _glfwTerminateOSMesa(void)
+{
+    if (_glfw.osmesa.handle)
+    {
+        _glfw_dlclose(_glfw.osmesa.handle);
+        _glfw.osmesa.handle = NULL;
+    }
+}
+
+GLFWbool _glfwCreateContextOSMesa(_GLFWwindow* window,
+                                  const _GLFWctxconfig* ctxconfig,
+                                  const _GLFWfbconfig* fbconfig)
+{
+    OSMesaContext share;
+
+    if (ctxconfig->share)
+        share = ctxconfig->share->context.osmesa.handle;
+
+    // Initialize the context.
+    window->context.osmesa.buffer = NULL;
+    window->context.osmesa.width = 0;
+    window->context.osmesa.height = 0;
+
+    // Create to create an OSMesa context.
+    window->context.osmesa.handle = OSMesaCreateContext(OSMESA_RGBA, share);
+    if (window->context.osmesa.handle == 0)
+    {
+        _glfwInputError(GLFW_VERSION_UNAVAILABLE,
+                        "OSMesa: Failed to create context.");
+        return GLFW_FALSE;
+    }
+
+    // Set up the context API.
+    window->context.makeCurrent = makeContextCurrentOSMesa;
+    window->context.swapBuffers = swapBuffersOSMesa;
+    window->context.swapInterval = swapIntervalOSMesa;
+    window->context.extensionSupported = extensionSupportedOSMesa;
+    window->context.getProcAddress = getProcAddressOSMesa;
+    window->context.destroy = destroyContextOSMesa;
+
+    return GLFW_TRUE;
+}
+
+//////////////////////////////////////////////////////////////////////////
+//////                        GLFW native API                       //////
+//////////////////////////////////////////////////////////////////////////
+