(#26) Add experimental Live Update feature

README.md

@@ -30,6 +30,16 @@ $ ln -s /path/to/boomer/overlay/ boomer
 $ nix-env -iA nixos.boomer
 ```
 
+## Experimental Live Update
+
+See issue [#26]. For an experimental Live Update feature compile the application with the following flags:
+
+```console
+$ nimble build -d:live
+```
+
+The feature is really unstable and experimental, so use it at your own risk.
+
 ## References
 
 - https://github.com/nim-lang/x11/blob/bf9dc74dd196a98b7c2a2beea4d92640734f7c60/examples/x11ex.nim
@@ -46,3 +56,5 @@ You can support my work via
 
 - Twitch channel: https://www.twitch.tv/subs/tsoding
 - Patreon: https://www.patreon.com/tsoding
+
+[#26]: https://github.com/tsoding/boomer/issues/26

src/boomer.nim

@@ -393,4 +393,24 @@ proc main() =
     glXSwapBuffers(display, win)
     glFinish()
 
+    when defined(live):
+      screenshot = XGetSubImage(display, root,
+                                0, 0,
+                                screenshot.width.cuint,
+                                screenshot.height.cuint,
+                                AllPlanes,
+                                ZPixmap,
+                                screenshot,
+                                0, 0)
+      glTexImage2D(GL_TEXTURE_2D,
+                   0,
+                   GL_RGB.GLint,
+                   screenshot.width,
+                   screenshot.height,
+                   0,
+                   # TODO(#13): the texture format is hardcoded
+                   GL_BGRA,
+                   GL_UNSIGNED_BYTE,
+                   screenshot.data)
+
 main()