Draw the GuiVideoRenderer on a separate framebuffer that has the actual size of the window instead of MC's framebuffer which may have a different size

src/main/java/com/replaymod/render/rendering/VideoRenderer.java

@@ -20,6 +20,7 @@ import net.minecraft.client.Minecraft;
 import net.minecraft.client.audio.SoundCategory;
 import net.minecraft.client.gui.ScaledResolution;
 import net.minecraft.client.renderer.OpenGlHelper;
+import net.minecraft.client.shader.Framebuffer;
 import net.minecraft.util.Timer;
 import org.lwjgl.input.Mouse;
 import org.lwjgl.opengl.Display;
@@ -62,6 +63,9 @@ public class VideoRenderer implements RenderInfo {
     private boolean paused;
     private boolean cancelled;
 
+    private Framebuffer guiFramebuffer;
+    private int displayWidth, displayHeight;
+
     public VideoRenderer(RenderSettings settings, ReplayHandler replayHandler, Timeline timeline) throws IOException {
         this.settings = settings;
         this.replayHandler = replayHandler;
@@ -130,6 +134,13 @@ public class VideoRenderer implements RenderInfo {
 
     @Override
     public float updateForNextFrame() {
+        // because the jGui lib uses Minecraft's displayWidth and displayHeight values, update these temporarily
+        int displayWidthBefore = mc.displayWidth;
+        int displayHeightBefore = mc.displayHeight;
+
+        mc.displayWidth = displayWidth;
+        mc.displayHeight = displayHeight;
+
         if (!settings.isHighPerformance() || framesDone % fps == 0) {
             drawGui();
         }
@@ -142,6 +153,10 @@ public class VideoRenderer implements RenderInfo {
             tick();
         }
 
+        // change Minecraft's display size back
+        mc.displayWidth = displayWidthBefore;
+        mc.displayHeight = displayHeightBefore;
+
         framesDone++;
         return mc.timer.renderPartialTicks;
     }
@@ -192,10 +207,15 @@ public class VideoRenderer implements RenderInfo {
 
         totalFrames = (int) (duration*fps/1000);
 
-        ScaledResolution scaled = new ScaledResolution(mc, mc.displayWidth, mc.displayHeight);
+        updateDisplaySize();
+
+        ScaledResolution scaled = new ScaledResolution(mc, displayWidth, displayHeight);
         gui.toMinecraft().setWorldAndResolution(mc, scaled.getScaledWidth(), scaled.getScaledHeight());
 
         chunkLoadingRenderGlobal = new ChunkLoadingRenderGlobal(mc.renderGlobal);
+
+        // Set up our own framebuffer to render the GUI to
+        guiFramebuffer = new Framebuffer(displayWidth, displayHeight, true);
     }
 
     private void finish() {
@@ -219,6 +239,9 @@ public class VideoRenderer implements RenderInfo {
         ReplayMod.soundHandler.playRenderSuccessSound();
 
         new GuiRenderingDone(ReplayModRender.instance, videoWriter.getVideoFile(), totalFrames, settings).display();
+
+        // Finally, resize the Minecraft framebuffer to the actual width/height of the window
+        mc.resize(displayWidth, displayHeight);
     }
 
     private void tick() {
@@ -238,12 +261,22 @@ public class VideoRenderer implements RenderInfo {
 
     public void drawGui() {
         do {
+            // Resize the GUI framebuffer if the display size changed
+            if (!settings.isHighPerformance() && displaySizeChanged()) {
+                updateDisplaySize();
+                guiFramebuffer.createBindFramebuffer(mc.displayWidth, mc.displayHeight);
+            }
+
             pushMatrix();
             clear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
             enableTexture2D();
-            mc.getFramebuffer().bindFramebuffer(true);
+            guiFramebuffer.bindFramebuffer(true);
+
             mc.entityRenderer.setupOverlayRendering();
 
+            ScaledResolution scaled = new ScaledResolution(mc, mc.displayWidth, mc.displayHeight);
+            gui.toMinecraft().setWorldAndResolution(mc, scaled.getScaledWidth(), scaled.getScaledHeight());
+
             try {
                 gui.toMinecraft().handleInput();
             } catch (IOException e) {
@@ -252,18 +285,17 @@ public class VideoRenderer implements RenderInfo {
                 throw new RuntimeException(e);
             }
 
-            ScaledResolution scaled = new ScaledResolution(mc, mc.displayWidth, mc.displayHeight);
             int mouseX = Mouse.getX() * scaled.getScaledWidth() / mc.displayWidth;
             int mouseY = scaled.getScaledHeight() - Mouse.getY() * scaled.getScaledHeight() / mc.displayHeight - 1;
+
             gui.toMinecraft().drawScreen(mouseX, mouseY, 0);
 
-            mc.getFramebuffer().unbindFramebuffer();
+            guiFramebuffer.unbindFramebuffer();
             popMatrix();
             pushMatrix();
-            mc.getFramebuffer().framebufferRender(mc.displayWidth, mc.displayHeight);
+            guiFramebuffer.framebufferRender(displayWidth, displayHeight);
             popMatrix();
 
-
             // if not in high performance mode, update the gui size if screen size changed
             // otherwise just swap the progress gui to screen
             if (settings.isHighPerformance()) {
@@ -285,6 +317,15 @@ public class VideoRenderer implements RenderInfo {
         } while (paused);
     }
 
+    private boolean displaySizeChanged() {
+        return displayWidth != Display.getWidth() || displayHeight != Display.getHeight();
+    }
+
+    private void updateDisplaySize() {
+        displayWidth = Display.getWidth();
+        displayHeight = Display.getHeight();
+    }
+
     public int getFramesDone() {
         return framesDone;
     }