(#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

@@ -151,7 +151,7 @@ proc main() =
   echo "Screen rate: ", rate
 
   var screenshot = takeScreenshot(display, root)
-  assert screenshot.bpp == 32
+  assert screenshot.bits_per_pixel == 32
 
   let screen = XDefaultScreen(display)
   var glxMajor, glxMinor: int
@@ -264,7 +264,7 @@ proc main() =
                # TODO(#13): the texture format is hardcoded
                GL_BGRA,
                GL_UNSIGNED_BYTE,
-               screenshot.pixels)
+               screenshot.data)
   glGenerateMipmap(GL_TEXTURE_2D)
 
   glUniform1i(glGetUniformLocation(shaderProgram, "tex".cstring), 0)
@@ -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()

src/image.nim

@@ -1,8 +1,6 @@
 import x11/xlib, x11/x
 
-type Image* = object
-  width*, height*, bpp*: cint
-  pixels*: cstring
+type Image* = PXImage
 
 proc saveToPPM*(image: Image, filePath: string) =
   var f = open(filePath, fmWrite)
@@ -11,26 +9,21 @@ proc saveToPPM*(image: Image, filePath: string) =
   writeLine(f, image.width, " ", image.height)
   writeLine(f, 255)
   for i in 0..<(image.width * image.height):
-    f.write(image.pixels[i * 4 + 2])
-    f.write(image.pixels[i * 4 + 1])
-    f.write(image.pixels[i * 4 + 0])
+    f.write(image.data[i * 4 + 2])
+    f.write(image.data[i * 4 + 1])
+    f.write(image.data[i * 4 + 0])
 
 # NOTE: it's not possible to deallocate the returned Image because the
 # reference to XImage is lost.
 proc takeScreenshot*(display: PDisplay, root: TWindow): Image =
   var attributes: TXWindowAttributes
   discard XGetWindowAttributes(display, root, addr attributes)
 
-  var screenshot = XGetImage(display, root,
+  result = XGetImage(display, root,
                              0, 0,
                              attributes.width.cuint,
                              attributes.height.cuint,
                              AllPlanes,
                              ZPixmap)
-  if screenshot == nil:
+  if result == nil:
     quit "Could not get a screenshot"
-
-  result.width = attributes.width
-  result.height = attributes.height
-  result.bpp = screenshot.bits_per_pixel
-  result.pixels = screenshot.data