Implement scissors

smylib/fabric/src/main/java/net/smyler/smylib/gui/WrappedGuiGraphics.java

@@ -12,9 +12,9 @@
 import net.smyler.smylib.Color;
 import net.smyler.smylib.Identifier;
 import net.smyler.smylib.gui.gl.Blaze3dGlContext;
+import net.smyler.smylib.gui.gl.Gl20Scissor;
 import net.smyler.smylib.gui.gl.GlContext;
 import net.smyler.smylib.gui.gl.Scissor;
-import net.smyler.smylib.gui.gl.WrappedGuiGraphicsScissor;
 import net.smyler.smylib.gui.sprites.Sprite;
 import org.joml.Matrix4f;
 
@@ -25,7 +25,7 @@
 public class WrappedGuiGraphics implements UiDrawContext {
 
     public final GuiGraphics vanillaGraphics;
-    private final Scissor scissor = new WrappedGuiGraphicsScissor();
+    private final Scissor scissor = new Gl20Scissor();
     private final GlContext glState = new Blaze3dGlContext();
     private final TextureManager textureManager;
     private int dynamicTextureLocationCounter = 0;

smylib/fabric/src/main/java/net/smyler/smylib/gui/gl/Gl20Scissor.java

@@ -0,0 +1,94 @@
+package net.smyler.smylib.gui.gl;
+
+import net.smyler.smylib.game.GameClient;
+import org.lwjgl.opengl.GL20;
+
+import java.util.LinkedList;
+import java.util.List;
+
+import static java.lang.Math.*;
+import static net.smyler.smylib.SmyLib.getGameClient;
+
+/**
+ * A wrapper around OpenGL 2.0's scissor feature.
+ * For now, it's easier to rely on this rather than rendering to different frame buffers.
+ *
+ * @author Smyler
+ */
+public class Gl20Scissor implements Scissor {
+
+    private boolean isScissorEnabled = GL20.glIsEnabled(GL20.GL_SCISSOR_TEST);
+    private float x, y, width, height; // This is in the Minecraft screen coordinate space
+
+    private final List<ScissorStackFrame> scissorPosStack = new LinkedList<>();
+
+    @Override
+    public void setEnabled(boolean yesNo) {
+        if(yesNo && !this.isScissorEnabled) {
+            GL20.glEnable(GL20.GL_SCISSOR_TEST);
+        } else if(!yesNo && this.isScissorEnabled) {
+            GL20.glDisable(GL20.GL_SCISSOR_TEST);
+        }
+        this.isScissorEnabled = yesNo;
+    }
+
+    @Override
+    public boolean isEnabled() {
+        return this.isScissorEnabled;
+    }
+
+    @Override
+    public void cropScreen(float x, float y, float width, float height) {
+        this.x = x;
+        this.y = y;
+        this.width = width;
+        this.height = height;
+        doScissor();
+    }
+
+    @Override
+    public void cropSection(float x, float y, float width, float height) {
+        float intersectX = max(x, this.x);
+        float intersectY = max(y, this.y);
+        float intersectWidth = min(width + x, this.width + this.x) - intersectX;
+        float intersectHeight = min(height + y, this.height + this.y) - intersectY;
+        this.cropScreen(intersectX, intersectY, intersectWidth, intersectHeight);
+    }
+
+    @Override
+    public void push() {
+        this.scissorPosStack.add(new ScissorStackFrame(isEnabled(), x, y, width, height));
+    }
+
+    @Override
+    public void pop() {
+        this.restore(this.scissorPosStack.removeLast());
+        this.doScissor();
+    }
+
+    private void doScissor() {
+        GameClient game = getGameClient();
+        float screenWidth = game.windowWidth();
+        float screenHeight = game.windowHeight();
+        double scale = game.scaleFactor();
+        float leftX = clamp(this.x, 0f, screenWidth);
+        float topY = clamp(screenHeight - this.y - this.height, 0f, screenHeight);
+        float rightX = clamp(this.x + this.width, 0f, screenWidth);
+        float bottomY = clamp(screenHeight - this.y, 0f, screenHeight);
+        float width = rightX - leftX;
+        float height = bottomY - topY;
+        GL20.glScissor((int) round(leftX * scale), (int) round(topY * scale), (int) round(width * scale), (int) round(height * scale));
+    }
+
+    private void restore(ScissorStackFrame frame) {
+        this.setEnabled(frame.enabled);
+        this.x = frame.x;
+        this.y = frame.y;
+        this.width = frame.width;
+        this.height = frame.height;
+    }
+
+    private record ScissorStackFrame(boolean enabled, float x, float y, float width, float height) {
+    }
+
+}

smylib/fabric/src/main/java/net/smyler/smylib/gui/screen/VanillaScreenProxy.java

@@ -33,6 +33,7 @@ public void render(GuiGraphics guiGraphics, int x, int y, float partialTicks) {
 
         this.screen.onUpdate(mouseX, mouseY, null);
         this.drawBackground(guiGraphics);
+        uiDrawContext.scissor().cropScreen(-1f, -1f, this.width + 1f, height + 1f);
         super.render(guiGraphics, x, y, partialTicks);
         this.screen.draw(uiDrawContext, 0, 0, mouseX, mouseY, true, true, null);
     }