Added tests/transparent_threads.c.

This is a minor variant of tests/threads.c that uses transparent windows.  You
should be able to drag the windows around and see whatever is behind them.

tests/CMakeLists.txt

@@ -37,13 +37,14 @@ add_executable(empty WIN32 MACOSX_BUNDLE empty.c ${TINYCTHREAD} ${GLAD})
 add_executable(sharing WIN32 MACOSX_BUNDLE sharing.c ${GLAD})
 add_executable(tearing WIN32 MACOSX_BUNDLE tearing.c ${GETOPT} ${GLAD})
 add_executable(threads WIN32 MACOSX_BUNDLE threads.c ${TINYCTHREAD} ${GLAD})
+add_executable(transparent_threads WIN32 MACOSX_BUNDLE transparent_threads.c ${TINYCTHREAD} ${GLAD})
 add_executable(title WIN32 MACOSX_BUNDLE title.c ${GLAD})
 add_executable(windows WIN32 MACOSX_BUNDLE windows.c ${GLAD})
 
 target_link_libraries(empty "${CMAKE_THREAD_LIBS_INIT}" "${RT_LIBRARY}")
 target_link_libraries(threads "${CMAKE_THREAD_LIBS_INIT}" "${RT_LIBRARY}")
 
-set(WINDOWS_BINARIES empty sharing tearing threads title windows)
+set(WINDOWS_BINARIES empty sharing tearing threads transparent_threads title windows)
 set(CONSOLE_BINARIES clipboard events msaa gamma glfwinfo
                      iconify joysticks monitors reopen cursor)
 
@@ -61,6 +62,7 @@ if (APPLE)
     set_target_properties(sharing PROPERTIES MACOSX_BUNDLE_BUNDLE_NAME "Sharing")
     set_target_properties(tearing PROPERTIES MACOSX_BUNDLE_BUNDLE_NAME "Tearing")
     set_target_properties(threads PROPERTIES MACOSX_BUNDLE_BUNDLE_NAME "Threads")
+    set_target_properties(transparent_threads PROPERTIES MACOSX_BUNDLE_BUNDLE_NAME "Transparent threads")
     set_target_properties(title PROPERTIES MACOSX_BUNDLE_BUNDLE_NAME "Title")
     set_target_properties(windows PROPERTIES MACOSX_BUNDLE_BUNDLE_NAME "Windows")
 

tests/transparent_threads.c

@@ -0,0 +1,147 @@
+//========================================================================
+// Multi-threading test
+// Copyright (c) Camilla Berglund <elmindreda@elmindreda.org>
+//
+// This software is provided 'as-is', without any express or implied
+// warranty. In no event will the authors be held liable for any damages
+// arising from the use of this software.
+//
+// Permission is granted to anyone to use this software for any purpose,
+// including commercial applications, and to alter it and redistribute it
+// freely, subject to the following restrictions:
+//
+// 1. The origin of this software must not be misrepresented; you must not
+//    claim that you wrote the original software. If you use this software
+//    in a product, an acknowledgment in the product documentation would
+//    be appreciated but is not required.
+//
+// 2. Altered source versions must be plainly marked as such, and must not
+//    be misrepresented as being the original software.
+//
+// 3. This notice may not be removed or altered from any source
+//    distribution.
+//
+//========================================================================
+//
+// This test is intended to verify whether the OpenGL context part of
+// the GLFW API is able to be used from multiple threads
+//
+//========================================================================
+
+#include "tinycthread.h"
+
+#include <glad/glad.h>
+#include <GLFW/glfw3.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+typedef struct
+{
+    GLFWwindow* window;
+    const char* title;
+    float r, g, b, a;
+    thrd_t id;
+} Thread;
+
+static volatile int running = GLFW_TRUE;
+
+static void error_callback(int error, const char* description)
+{
+    fprintf(stderr, "Error: %s\n", description);
+}
+
+static int thread_main(void* data)
+{
+    const Thread* thread = data;
+
+    glfwMakeContextCurrent(thread->window);
+    glfwSwapInterval(1);
+
+    while (running)
+    {
+        const float v = (float) fabs(sin(glfwGetTime() * 2.f));
+        glClearColor(thread->r * v, thread->g * v, thread->b * v, thread->a * v);
+
+        glClear(GL_COLOR_BUFFER_BIT);
+        glfwSwapBuffers(thread->window);
+    }
+
+    glfwMakeContextCurrent(NULL);
+    return 0;
+}
+
+int main(void)
+{
+    int i, result;
+    Thread threads[] =
+    {
+        { NULL, "Red",   1.0f, 0.0f, 0.0f, 0.5f, 0 },
+        { NULL, "Green", 0.0f, 1.0f, 0.0f, 0.5f, 0 },
+        { NULL, "Blue",  0.0f, 0.0f, 1.0f, 0.5f, 0 }
+    };
+    const int count = sizeof(threads) / sizeof(Thread);
+
+    glfwSetErrorCallback(error_callback);
+
+    if (!glfwInit())
+        exit(EXIT_FAILURE);
+
+    glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE);
+
+    glfwWindowHint(GLFW_ALPHA_BITS, 8);
+    glfwWindowHint(GLFW_ALPHA_MASK, GLFW_TRUE);
+    glfwWindowHint(GLFW_DECORATED, GLFW_TRUE);
+
+    for (i = 0;  i < count;  i++)
+    {
+        threads[i].window = glfwCreateWindow(200, 200,
+                                             threads[i].title,
+                                             NULL, NULL);
+        if (!threads[i].window)
+        {
+            glfwTerminate();
+            exit(EXIT_FAILURE);
+        }
+
+        glfwSetWindowPos(threads[i].window, 200 + 250 * i, 200);
+        glfwShowWindow(threads[i].window);
+    }
+
+    glfwMakeContextCurrent(threads[0].window);
+    gladLoadGLLoader((GLADloadproc) glfwGetProcAddress);
+    glfwMakeContextCurrent(NULL);
+
+    for (i = 0;  i < count;  i++)
+    {
+        if (thrd_create(&threads[i].id, thread_main, threads + i) !=
+            thrd_success)
+        {
+            fprintf(stderr, "Failed to create secondary thread\n");
+
+            glfwTerminate();
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    while (running)
+    {
+        glfwWaitEvents();
+
+        for (i = 0;  i < count;  i++)
+        {
+            if (glfwWindowShouldClose(threads[i].window))
+                running = GLFW_FALSE;
+        }
+    }
+
+    for (i = 0;  i < count;  i++)
+        glfwHideWindow(threads[i].window);
+
+    for (i = 0;  i < count;  i++)
+        thrd_join(threads[i].id, &result);
+
+    exit(EXIT_SUCCESS);
+}
+