Merge pull request #51 from tsoding/48

(#48) Make it zoom towards the center of the screen

src/boomer.nim

@@ -65,7 +65,8 @@ proc newShaderProgram(vertex, fragment: Shader): GLuint =
 
   glUseProgram(result)
 
-proc draw(screenshot: Image, camera: var Camera, shader, vao, texture: GLuint) =
+proc draw(screenshot: Image, camera: var Camera, shader, vao, texture: GLuint,
+          windowSize: Vec2f, mouse: Mouse) =
   glClearColor(0.1, 0.1, 0.1, 1.0)
   glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT)
 
@@ -73,6 +74,15 @@ proc draw(screenshot: Image, camera: var Camera, shader, vao, texture: GLuint) =
 
   glUniform2f(glGetUniformLocation(shader, "cameraPos".cstring), camera.position[0], camera.position[1])
   glUniform1f(glGetUniformLocation(shader, "cameraScale".cstring), camera.scale)
+  glUniform2f(glGetUniformLocation(shader, "screenshotSize".cstring),
+              screenshot.width.float32,
+              screenshot.height.float32)
+  glUniform2f(glGetUniformLocation(shader, "windowSize".cstring),
+              windowSize.x.float32,
+              windowSize.y.float32)
+  glUniform2f(glGetUniformLocation(shader, "cursorPos".cstring),
+              mouse.curr.x.float32,
+              mouse.curr.y.float32)
 
   glBindVertexArray(vao)
   glDrawElements(GL_TRIANGLES, count = 6, GL_UNSIGNED_INT, indices = nil)
@@ -176,14 +186,16 @@ proc main() =
 
   var shaderProgram = newShaderProgram(vertexShader, fragmentShader)
 
+  let w = screenshot.width.float32
+  let h = screenshot.height.float32
   var
     vao, vbo, ebo: GLuint
     vertices = [
       # Position                 Texture coords
-      [GLfloat  1.0,  -1.0, 0.0, 1.0, 1.0], # Top right
-      [GLfloat  1.0,  1.0,  0.0, 1.0, 0.0], # Bottom right
-      [GLfloat -1.0,  1.0,  0.0, 0.0, 0.0], # Bottom left
-      [GLfloat -1.0,  -1.0, 0.0, 0.0, 1.0]  # Top left
+      [GLfloat    w,     0, 0.0, 1.0, 1.0], # Top right
+      [GLfloat    w,     h, 0.0, 1.0, 0.0], # Bottom right
+      [GLfloat    0,     h, 0.0, 0.0, 0.0], # Bottom left
+      [GLfloat    0,     0, 0.0, 0.0, 1.0]  # Top left
     ]
     indices = [GLuint(0), 1, 3,
                       1,  2, 3]
@@ -233,7 +245,6 @@ proc main() =
 
   glUniform1i(glGetUniformLocation(shaderProgram, "tex".cstring), 0)
 
-
   glEnable(GL_TEXTURE_2D)
 
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
@@ -241,8 +252,6 @@ proc main() =
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER)
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER)
 
-  glViewport(0, 0, screenshot.width, screenshot.height)
-
   var
     quitting = false
     camera = Camera(scale: 1.0)
@@ -251,6 +260,7 @@ proc main() =
   while not quitting:
     var wa: TXWindowAttributes
     discard XGetWindowAttributes(display, win, addr wa)
+    glViewport(0, 0, wa.width, wa.height)
 
     var xev: TXEvent
     while XPending(display) > 0:
@@ -264,9 +274,10 @@ proc main() =
                           xev.xmotion.y.float32)
 
         if mouse.drag:
-          let delta = world(mouse.prev, screenshot, camera) - world(mouse.curr, screenshot, camera)
+          let delta = world(camera, mouse.prev) - world(camera, mouse.curr)
           camera.position += delta
           camera.velocity = delta * config.dragVelocityFactor
+
         mouse.prev = mouse.curr
 
       of ClientMessage:
@@ -315,7 +326,9 @@ proc main() =
 
     camera.update(config, 1.0 / config.fps.float, mouse, screenshot)
 
-    screenshot.draw(camera, shaderProgram, vao, texture)
+    screenshot.draw(camera, shaderProgram, vao, texture,
+                    vec2(wa.width.float32, wa.height.float32),
+                    mouse)
 
     glXSwapBuffers(display, win)
 

src/config.nim

@@ -10,7 +10,8 @@ type Config* = object
 const defaultConfig* = Config(
   scrollSpeed: 1.0,
   dragVelocityFactor: 10.0,
-  dragFriction: 1.0,
+  # TODO: For a natual feel dragFriction probably should depend on velocity
+  dragFriction: 600.0,
   scaleFriction: 10.0,
   fps: 60
 )

src/la.nim

@@ -7,6 +7,9 @@ proc vec2*(x: float32, y: float32): Vec2f = (x, y)
 proc `*`*(a: Vec2f, s: float32): Vec2f =
   vec2(a.x * s, a.y * s)
 
+proc `/`*(a: Vec2f, s: float32): Vec2f =
+  vec2(a.x / s, a.y / s)
+
 proc `*`*(a: Vec2f, b: Vec2f): Vec2f =
   vec2(a.x * b.x, a.y * b.y)
 

src/navigation.nim

@@ -14,12 +14,8 @@ type Camera* = object
   scale*: float32
   deltaScale*: float
 
-proc world*(point: Vec2f, image: Image, camera: Camera): Vec2f =
-  let f = (camera.position + vec2(1.0f32, 1.0f32)) / vec2(2.0f32, 2.0f32)
-  let ps = vec2(image.width.float32 * camera.scale, image.height.float32 * camera.scale) * f
-  let ms = vec2(point.x.float32, point.y.float32) + ps
-  return vec2(ms.x / (image.width.float32 * camera.scale) * 2.0f32 - 1.0f32,
-              ms.y / (image.height.float32 * camera.scale) * 2.0f32 - 1.0f32)
+proc world*(camera: Camera, v: Vec2f): Vec2f =
+  (camera.position + v) / camera.scale
 
 proc update*(camera: var Camera, config: Config, dt: float, mouse: Mouse, image: Image) =
   if abs(camera.deltaScale) > 0.5:

src/vert.glsl

@@ -2,10 +2,24 @@
 in vec3 aPos;
 in vec2 aTexCoord;
 out vec2 texcoord;
+
 uniform vec2 cameraPos;
 uniform float cameraScale;
+uniform vec2 windowSize;
+uniform vec2 screenshotSize;
+uniform vec2 cursorPos;
+
+vec3 to_world(vec3 v) {
+    vec2 ratio = vec2(
+        windowSize.x / screenshotSize.x / cameraScale,
+        windowSize.y / screenshotSize.y / cameraScale);
+    return vec3((v.x / screenshotSize.x * 2.0 - 1.0) / ratio.x,
+                (v.y / screenshotSize.y * 2.0 - 1.0) / ratio.y,
+                v.z);
+}
+
 void main()
 {
-	gl_Position = vec4((aPos.x - cameraPos.x) * cameraScale, (aPos.y + cameraPos.y) * cameraScale, 0.0, 1.0);
+	gl_Position = vec4(to_world((aPos - vec3(cameraPos * vec2(1.0, -1.0), 0.0))), 1.0);
 	texcoord = aTexCoord;
 }