Use window texture (xcomposite) for background if the window is fullscreen on the selected monitor

src/window_texture.c

@@ -0,0 +1,138 @@
+#include "../include/window_texture.h"
+#include <X11/extensions/Xcomposite.h>
+#include <mgl/mgl.h>
+#include <stdio.h>
+
+#define EGL_IMAGE_PRESERVED_KHR 0x30D2
+#define EGL_TRUE 1
+#define EGL_NATIVE_PIXMAP_KHR 0x30B0
+
+static int x11_supports_composite_named_window_pixmap(Display *display) {
+    int extension_major;
+    int extension_minor;
+    if(!XCompositeQueryExtension(display, &extension_major, &extension_minor))
+        return 0;
+
+    int major_version;
+    int minor_version;
+    return XCompositeQueryVersion(display, &major_version, &minor_version) && (major_version > 0 || minor_version >= 2);
+}
+
+int window_texture_init(WindowTexture *window_texture, Display *display, void *egl_display, uint64_t window, egl_functions egl_funcs) {
+    window_texture->display = display;
+    window_texture->egl_display = egl_display;
+    window_texture->window = window;
+    window_texture->pixmap = None;
+    window_texture->texture_id = 0;
+    window_texture->redirected = 0;
+    window_texture->egl_funcs = egl_funcs;
+    
+    if(!x11_supports_composite_named_window_pixmap(display))
+        return 1;
+
+    XCompositeRedirectWindow(display, window, CompositeRedirectAutomatic);
+    window_texture->redirected = 1;
+    return window_texture_on_resize(window_texture);
+}
+
+static void window_texture_cleanup(WindowTexture *self, int delete_texture) {
+    mgl_context *context = mgl_get_context();
+
+    if(delete_texture && self->texture_id) {
+        context->gl.glDeleteTextures(1, &self->texture_id);
+        self->texture_id = 0;
+    }
+
+    if(self->pixmap) {
+        XFreePixmap(self->display, self->pixmap);
+        self->pixmap = None;
+    }
+}
+
+void window_texture_deinit(WindowTexture *self) {
+    if(self->redirected) {
+        XCompositeUnredirectWindow(self->display, self->window, CompositeRedirectAutomatic);
+        self->redirected = 0;
+    }
+    window_texture_cleanup(self, 1);
+}
+
+int window_texture_on_resize(WindowTexture *self) {
+    window_texture_cleanup(self, 0);
+    mgl_context *context = mgl_get_context();
+
+    int result = 0;
+    Pixmap pixmap = None;
+    unsigned int texture_id = 0;
+    void *image = NULL;
+
+    const intptr_t pixmap_attrs[] = {
+        EGL_IMAGE_PRESERVED_KHR, EGL_TRUE,
+        EGL_NONE,
+    };
+
+    pixmap = XCompositeNameWindowPixmap(self->display, self->window);
+    if(!pixmap) {
+        result = 2;
+        goto cleanup;
+    }
+
+    if(self->texture_id == 0) {
+        context->gl.glGenTextures(1, &texture_id);
+        if(texture_id == 0) {
+            result = 4;
+            goto cleanup;
+        }
+        context->gl.glBindTexture(GL_TEXTURE_2D, texture_id);
+    } else {
+        context->gl.glBindTexture(GL_TEXTURE_2D, self->texture_id);
+    }
+
+    context->gl.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    context->gl.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+    context->gl.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    context->gl.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+ 
+    /*
+    float fLargest = 0.0f;
+    glGetFloatv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &fLargest);
+    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, fLargest);
+    */
+
+    while(context->gl.glGetError()) {}
+    while(self->egl_funcs.eglGetError() != EGL_SUCCESS) {}
+
+    image = self->egl_funcs.eglCreateImage(self->egl_display, NULL, EGL_NATIVE_PIXMAP_KHR, (void*)pixmap, pixmap_attrs);
+    if(!image) {
+        result = 4;
+        goto cleanup;
+    }
+
+    self->egl_funcs.glEGLImageTargetTexture2DOES(GL_TEXTURE_2D, image);
+    if(context->gl.glGetError() != 0 || self->egl_funcs.eglGetError() != EGL_SUCCESS) {
+        result = 5;
+        goto cleanup;
+    }
+
+    self->pixmap = pixmap;
+    self->texture_id = texture_id;
+
+    cleanup:
+    context->gl.glBindTexture(GL_TEXTURE_2D, 0);
+
+    if(image)
+        self->egl_funcs.eglDestroyImage(self->egl_display, image);
+
+    if(result != 0) {
+        if(texture_id != 0)
+            context->gl.glDeleteTextures(1, &texture_id);
+        if(pixmap)
+            XFreePixmap(self->display, pixmap);
+    }
+
+    return result;
+}
+
+unsigned int window_texture_get_opengl_texture_id(WindowTexture *self) {
+    return self->texture_id;
+}