Add demo.nim to be used for active (keyboard, mouse, screen) demos. (#151)

src/pixie/demo.nim

@@ -0,0 +1,74 @@
+import staticglfw, opengl, pixie
+export pixie, staticglfw
+
+var
+  screen* = newImage(800, 600)
+  window*: Window
+
+proc getMousePos*(): Vec2 =
+  ## Get the mouse position.
+  var xpos, ypos: float64
+  getCursorPos(window, xpos.addr, ypos.addr)
+  vec2(xpos, ypos)
+
+proc isMouseDown*(): bool =
+  ## Get if the left mouse button is down.
+  getMouseButton(window, MOUSE_BUTTON_LEFT) == PRESS
+
+proc isKeyDown*(keyCode: int): bool =
+  ## Get if the key is currently being held down.
+  ## See key codes: https://www.glfw.org/docs/3.3/group__keys.html
+  ## Examples: KEY_SPACE, KEY_UP, KEY_DOWN, KEY_LEFT, KEY_RIGHT
+  getKey(window, keyCode.cint) == PRESS
+
+proc tick*() =
+  ## Called this every frame in a while loop.
+
+  # Update texture with new pixels from surface.
+  var dataPtr = screen.data[0].addr
+  glTexSubImage2D(
+    GL_TEXTURE_2D, 0, 0, 0,
+    screen.width.GLsizei, screen.height.GLsizei,
+    GL_RGBA, GL_UNSIGNED_BYTE, dataPtr
+  )
+
+  # Draw a quad over the whole screen.
+  glClear(GL_COLOR_BUFFER_BIT)
+  glBegin(GL_QUADS)
+  glTexCoord2d(0.0, 0.0); glVertex2d(-1.0, +1.0)
+  glTexCoord2d(1.0, 0.0); glVertex2d(+1.0, +1.0)
+  glTexCoord2d(1.0, 1.0); glVertex2d(+1.0, -1.0)
+  glTexCoord2d(0.0, 1.0); glVertex2d(-1.0, -1.0)
+  glEnd()
+
+  swapBuffers(window)
+
+  pollEvents()
+
+  if windowShouldClose(window) == 1:
+    quit()
+
+proc start*(title = "Demo") =
+  ## Start the demo.
+  if init() == 0:
+    quit("Failed to Initialize GLFW.")
+
+  windowHint(RESIZABLE, false.cint)
+  window = createWindow(screen.width.cint, screen.height.cint, title, nil, nil)
+  if window == nil:
+    quit("Failed to create window.")
+  makeContextCurrent(window)
+  loadExtensions()
+
+  # Allocate a texture and bind it.
+  var dataPtr = screen.data[0].addr
+  glTexImage2D(
+    GL_TEXTURE_2D, 0, 3,
+    screen.width.GLsizei, screen.height.GLsizei,
+    0, GL_RGBA, GL_UNSIGNED_BYTE, dataPtr
+  )
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP)
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP)
+  glEnable(GL_TEXTURE_2D)