Ensure correct blending function for transparent window

8 files changed, 48 insertions, 5 deletions

diff --git a/include/mgl/gl_macro.h b/include/mgl/gl_macro.h
index cbecf94..ba2d3f1 100644
--- a/include/mgl/gl_macro.h
+++ b/include/mgl/gl_macro.h
@@ -18,6 +18,7 @@
 
 #define GL_COLOR_BUFFER_BIT 0x00004000
 #define GL_BLEND 0x0BE2
+#define GL_ONE 1
 #define GL_SRC_ALPHA 0x0302
 #define GL_ONE_MINUS_SRC_ALPHA 0x0303
 #define GL_TEXTURE_2D 0x0DE1
diff --git a/include/mgl/mgl.h b/include/mgl/mgl.h
index 4e1a181..e314e03 100644
--- a/include/mgl/mgl.h
+++ b/include/mgl/mgl.h
@@ -6,10 +6,13 @@
 /* Display* on x11 */
 typedef void* mgl_connection;
 typedef struct mgl_context mgl_context;
+typedef struct mgl_window mgl_window;
 
 struct mgl_context {
     mgl_connection connection;
     mgl_gl gl;
+    mgl_window *current_window;
+
     unsigned long wm_delete_window_atom;
     unsigned long net_wm_ping_atom;
     unsigned long net_wm_pid_atom;
diff --git a/include/mgl/window/window.h b/include/mgl/window/window.h
index eb7f587..23b780a 100644
--- a/include/mgl/window/window.h
+++ b/include/mgl/window/window.h
@@ -74,7 +74,7 @@ typedef struct {
     mgl_window_handle parent_window;         /* 0 = root window */
     bool hidden;                             /* false by default */
     bool override_redirect;                  /* false by default */
-    bool support_alpha;                      /* support alpha for the window, false by default */
+    bool support_alpha;                      /* support alpha for the window, false by default. If this is set to true then you need to call mgl_window_set_texture_blend_func before rendering textures and call mgl_window_set_render_blend_func afterwards to ensure correct alpha blending */
     bool hide_decorations;                   /* this is a hint, it may be ignored by the window manager, false by default */
     mgl_color background_color;              /* default: black */
     const char *class_name;
@@ -165,6 +165,9 @@ bool mgl_window_get_clipboard(mgl_window *self, mgl_clipboard_callback callback,
 bool mgl_window_get_clipboard_string(mgl_window *self, char **str, size_t *size);
 void mgl_window_set_key_repeat_enabled(mgl_window *self, bool enabled);
 
+void mgl_window_set_texture_blend_func(mgl_window *self);
+void mgl_window_set_render_blend_func(mgl_window *self);
+
 void mgl_window_flush(mgl_window *self);
 
 #endif /* MGL_WINDOW_H */
diff --git a/src/graphics/sprite.c b/src/graphics/sprite.c
index 3110cf9..613ec4c 100644
--- a/src/graphics/sprite.c
+++ b/src/graphics/sprite.c
@@ -1,5 +1,6 @@
 #include "../../include/mgl/graphics/sprite.h"
 #include "../../include/mgl/graphics/texture.h"
+#include "../../include/mgl/window/window.h"
 #include "../../include/mgl/mgl.h"
 
 void mgl_sprite_init(mgl_sprite *self, mgl_texture *texture) {
@@ -60,6 +61,8 @@ void mgl_sprite_draw(mgl_context *context, mgl_sprite *sprite) {
     if(!sprite->texture)
         return;
 
+    mgl_window_set_texture_blend_func(context->current_window);
+
     float texture_right = 1.0f;
     float texture_bottom = 1.0f;
     if(sprite->texture->pixel_coordinates) {
@@ -86,4 +89,6 @@ void mgl_sprite_draw(mgl_context *context, mgl_sprite *sprite) {
     context->gl.glEnd();
     mgl_texture_use(NULL);
     context->gl.glLoadIdentity(); /* TODO: Remove, but what about glRotatef above */
+
+    mgl_window_set_render_blend_func(context->current_window);
 }
diff --git a/src/graphics/text.c b/src/graphics/text.c
index 0942b62..76ac128 100644
--- a/src/graphics/text.c
+++ b/src/graphics/text.c
@@ -1,6 +1,7 @@
 #include "../../include/mgl/graphics/text.h"
 #include "../../include/mgl/graphics/font.h"
 #include "../../include/mgl/system/utf8.h"
+#include "../../include/mgl/window/window.h"
 #include "../../include/mgl/mgl.h"
 #include <stdio.h>
 
@@ -225,10 +226,14 @@ void mgl_text_draw(mgl_context *context, mgl_text *text) {
     text_draw_userdata.context = context;
     text_draw_userdata.prev_codepoint = 0;
 
+    mgl_window_set_texture_blend_func(context->current_window);
+
     context->gl.glColor4ub(text->color.r, text->color.g, text->color.b, text->color.a);
     mgl_texture_use(&text->font->texture);
     context->gl.glBegin(GL_QUADS);
     mgl_text_for_each_codepoint(text, text_draw_callback, &text_draw_userdata);
     context->gl.glEnd();
     mgl_texture_use(NULL);
+
+    mgl_window_set_render_blend_func(context->current_window);
 }
diff --git a/src/mgl.c b/src/mgl.c
index 16379e0..6fd26a7 100644
--- a/src/mgl.c
+++ b/src/mgl.c
@@ -119,6 +119,8 @@ void mgl_deinit(void) {
             */
             mgl_gl_unload(&context.gl);
         }
+
+        context.current_window = NULL;
     }
 
     if(init_count > 0)
diff --git a/src/window/window.c b/src/window/window.c
index 586719d..ccbf8ef 100644
--- a/src/window/window.c
+++ b/src/window/window.c
@@ -85,6 +85,7 @@ typedef struct {
     GLXFBConfig *fbconfigs;
     GLXFBConfig fbconfig;
     XVisualInfo *visual_info;
+    bool support_alpha;
 
     /* This only contains connected and active monitors */
     mgl_monitor monitors[MAX_MONITORS];
@@ -185,6 +186,7 @@ static int x11_context_init(x11_context *self, bool alpha) {
     self->fbconfigs = NULL;
     self->fbconfig = NULL;
     self->visual_info = NULL;
+    self->support_alpha = alpha;
 
     memset(self->monitors, 0, sizeof(self->monitors));
     self->num_monitors = 0;
@@ -574,6 +576,7 @@ static int mgl_window_init(mgl_window *self, const char *title, const mgl_window
     self->num_monitors = 0;
 
     mgl_context *context = mgl_get_context();
+    context->current_window = self;
 
     Window parent_window = params ? params->parent_window : None;
     if(parent_window == 0)
@@ -700,7 +703,7 @@ static int mgl_window_init(mgl_window *self, const char *title, const mgl_window
     context->gl.glEnable(GL_TEXTURE_2D);
     context->gl.glEnable(GL_BLEND);
     context->gl.glEnable(GL_SCISSOR_TEST);
-    context->gl.glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+    mgl_window_set_render_blend_func(self);
     context->gl.glEnableClientState(GL_VERTEX_ARRAY);
     context->gl.glEnableClientState(GL_TEXTURE_COORD_ARRAY);
     context->gl.glEnableClientState(GL_COLOR_ARRAY);
@@ -765,6 +768,10 @@ void mgl_window_deinit(mgl_window *self) {
     self->clipboard_size = 0;
 
     self->open = false;
+
+    mgl_context *context = mgl_get_context();
+    if(context->current_window == self)
+        context->current_window = NULL;
 }
 
 /* Returns MGL_KEY_UNKNOWN on no match */
@@ -1256,7 +1263,13 @@ static void mgl_window_on_receive_event(mgl_window *self, XEvent *xev, mgl_event
 
 void mgl_window_clear(mgl_window *self, mgl_color color) {
     mgl_context *context = mgl_get_context();
-    context->gl.glClearColor((float)color.r / 255.0f, (float)color.g / 255.0f, (float)color.b / 255.0f, (float)color.a / 255.0f);
+    x11_context *x11_context = self->context;
+
+    const float alpha = (float)color.a / 255.0f;
+    if(x11_context->support_alpha)
+        context->gl.glClearColor(((float)color.r / 255.0f) * alpha, ((float)color.g / 255.0f) * alpha, ((float)color.b / 255.0f) * alpha, alpha);
+    else
+        context->gl.glClearColor((float)color.r / 255.0f, (float)color.g / 255.0f, (float)color.b / 255.0f, alpha);
     context->gl.glClear(GL_COLOR_BUFFER_BIT);
 }
 
@@ -1783,6 +1796,17 @@ void mgl_window_set_key_repeat_enabled(mgl_window *self, bool enabled) {
     self->key_repeat_enabled = enabled;
 }
 
+void mgl_window_set_texture_blend_func(mgl_window *self) {
+    mgl_context *context = mgl_get_context();
+    context->gl.glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+}
+
+void mgl_window_set_render_blend_func(mgl_window *self) {
+    mgl_context *context = mgl_get_context();
+    x11_context *x11_context = self->context;
+    context->gl.glBlendFunc(x11_context->support_alpha ? GL_ONE : GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+}
+
 void mgl_window_flush(mgl_window *self) {
     mgl_context *context = mgl_get_context();
     XFlush(context->connection);
diff --git a/tests/main.c b/tests/main.c
index 720cf06..f52e3d4 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -220,7 +220,7 @@ static bool clipboard_callback(const unsigned char *data, size_t size, mgl_clipb
     return true;
 }
 
-int main(int argc, char **argv) {
+int main(void) {
     test_hash_map();
     test_utf8();
 
@@ -252,7 +252,7 @@ int main(int argc, char **argv) {
     if(mgl_texture_init(&texture) != 0)
         return 1;
 
-    if(mgl_texture_load_from_file(&texture, "tests/X11.jpg", &(mgl_texture_load_options){ false, false }) != 0)
+    if(mgl_texture_load_from_file(&texture, "tests/X11.jpg", &(mgl_texture_load_options){ .compressed = false, .pixel_coordinates = false, .mipmap = false }) != 0)
         return 1;
 
     if(mgl_mapped_file_load("/usr/share/fonts/TTF/Hack-Regular.ttf", &font_file, &(mgl_memory_mapped_file_load_options){ .readable = true, .writable = false }) != 0)