Handle window resizes correctly

src/org/dhsdev/flowerknight/FlowerKnight.java

@@ -36,6 +36,8 @@ public static void init() {
         // Set up GLFW. Errors should be checked here later.
         glfwInit();
 
+        glfwWindowHint(GLFW_RESIZABLE, GLFW_TRUE);
+
         // macOS needs to request a forward profile for a later
         // version of OpenGL explicitly. Version 3.3, to be specific.
         if (GetOSType.getOSType() == OSType.MACOS) {
@@ -55,6 +57,19 @@ public static void init() {
 
         Shader.getSpotlightShader().registerUniform("time");
 
+        // Register width and height for every shader
+        for (var shader : new Shader[] {
+                Shader.getGameShader(),
+                Shader.getSpotlightShader(),
+                Shader.getTrivialShader(),
+        }) {
+            shader.registerUniform("width");
+            shader.registerUniform("height");
+        }
+
+        // Update shaders here after all uniforms have been registered
+        window.updateShadersOnResize(window.width(), window.height());
+
         TextureAtlas.loadAllTextures();
 
     }
@@ -68,23 +83,11 @@ public static void mainloop() {
         // While it's open, clear screen and check for events.
         while (window.isOpen()) {
 
-            Shader.getSpotlightShader().bind();
-            Shader.getSpotlightShader().setUniform("time", (float) glfwGetTime());
-
-            Camera.updateShaders();
+            window.updateNeededShaders();
 
             GameObject.updateAll();
 
-            window.clear();
-
-            // Iterate and draw all renderable object
-            for (Renderable renderable : Renderable.renderables) {
-                renderable.draw();
-            }
-
-
-            // Render everything to screen at once
-            window.displayAllUpdates();
+            window.redraw();
 
             window.callEventHandlers();
 

src/org/dhsdev/flowerknight/gl/Window.java

@@ -1,5 +1,7 @@
 package org.dhsdev.flowerknight.gl;
 
+import org.dhsdev.flowerknight.game.Camera;
+import org.lwjgl.glfw.GLFWVidMode;
 import org.lwjgl.opengl.GL;
 
 import java.util.Objects;
@@ -29,9 +31,6 @@ public class Window {
      */
     public Window(int samples) {
 
-        // Right now the window is non-resizable.
-        glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);
-
         // Hint MSAA
         glfwWindowHint(GLFW_SAMPLES, samples);
 
@@ -42,13 +41,27 @@ public Window(int samples) {
         // Don't ask me what the two NULLs are for. I have no clue.
         handle = glfwCreateWindow(screenWidth, screenHeight, "FlowerKnight", NULL, NULL);
 
+        width  = screenWidth;
+        height = screenHeight;
+
         glfwMakeContextCurrent(handle);
         GL.createCapabilities();
 
         // Enable MSAA
         glEnable(GL_MULTISAMPLE);
 
         glfwShowWindow(handle);
+
+        // We want the window to immediately render as it is resized - the images
+        // will scale correctly, but the spotlight shader will freeze and the
+        // will not remain a square.
+        glfwSetWindowSizeCallback(handle, (long window, int width, int height) -> {
+            // Update the shaders and render.
+            updateShadersOnResize(width, height);
+            updateNeededShaders();
+            redraw();
+        });
+
     }
 
     /**
@@ -89,4 +102,80 @@ public void delete() {
         glfwDestroyWindow(handle);
     }
 
+    /**
+     * Update shader uniforms when the window gets resized.
+     * @param width the new window width
+     * @param height the new window height
+     */
+    public void updateShadersOnResize(float width, float height) {
+
+        this.width  = width;
+        this.height = height;
+
+        // Update width and height for every shader
+        for (var shader : new Shader[] {
+                Shader.getGameShader(),
+                Shader.getSpotlightShader(),
+                Shader.getTrivialShader(),
+        }) {
+            shader.bind();
+            shader.setUniform("width" , width);
+            shader.setUniform("height", height);
+        }
+
+    }
+
+    /**
+     * Window width
+     */
+    private float width;
+
+    /**
+     * Get width
+     */
+    public float width() {
+        return width;
+    }
+
+    /**
+     * Window height
+     */
+    private float height;
+
+    /**
+     * Get height
+     */
+    public float height() {
+        return height;
+    }
+
+    /**
+     * Render everything.
+     */
+    public void redraw() {
+
+        this.clear();
+
+        // Iterate and draw all renderable object
+        for (Renderable renderable : Renderable.renderables) {
+            renderable.draw();
+        }
+
+        // Render everything to screen at once
+        this.displayAllUpdates();
+
+    }
+
+    /**
+     * Update the spotlight annd camera shaders which change with every tick.
+     */
+    public void updateNeededShaders() {
+
+        Shader.getSpotlightShader().bind();
+        Shader.getSpotlightShader().setUniform("time", (float) glfwGetTime());
+
+        Camera.updateShaders();
+
+    }
+
 }

src/shader/game_vert.glsl

@@ -8,11 +8,24 @@ layout (location=1) in vec2 texCoord;
 uniform vec2 cameraLoc;
 uniform float zoom;
 
+// For a full explanation of these variables, see trivial_vert.glsl
+uniform float width, height;
+
 out vec2 outTexCoord;
 
 void main() {
+
     gl_Position = vec4(position, 1.0);
+
     gl_Position.xy -= cameraLoc; // Update with camera position
     gl_Position.xy /= zoom;
+
+    if (width < height) {
+        gl_Position.y *= (width / height);
+    } else {
+        gl_Position.x *= (height / width);
+    }
+
     outTexCoord = texCoord;
+
 }

src/shader/trivial_vert.glsl

@@ -5,7 +5,22 @@ layout (location=1) in vec2 texCoord;
 
 out vec2 outTexCoord;
 
+uniform float width, height;
+
 void main() {
+
     gl_Position = vec4(position, 1.0);
+
+    // Width and height are the width and height of the window. We want to have
+    // everything rendered in a square, so everything is rendered in the largest
+    // square possible. To do this, we scale the larger coordinate space down to
+    // the smaller one.
+    if (width < height) {
+        gl_Position.y *= (width / height);
+    } else {
+        gl_Position.x *= (height / width);
+    }
+
     outTexCoord = texCoord;
+
 }