From 6f5500d4e85613b4176e9afd3cf1b53df1aa77f9 Mon Sep 17 00:00:00 2001
From: UnknownShadow200 <unknownshadow200@gmail.com>
Date: Thu, 25 Apr 2024 22:07:33 +1000
Subject: [PATCH] Dreamcast: WIP on split screen support

---
 src/Graphics_Dreamcast.c     |  6 ++++++
 third_party/gldc/src/sh4.c   |  4 ++--
 third_party/gldc/src/state.c | 16 +++++-----------
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/src/Graphics_Dreamcast.c b/src/Graphics_Dreamcast.c
index e1a91a258..b0fce28ce 100644
--- a/src/Graphics_Dreamcast.c
+++ b/src/Graphics_Dreamcast.c
@@ -559,6 +559,12 @@ void Gfx_OnWindowResize(void) {
 }
 
 void Gfx_SetViewport(int x, int y, int w, int h) {
+	if (x == 0 && y == 0 && w == Game.Width && h == Game.Height) {
+		glDisable(GL_SCISSOR_TEST);
+	} else {
+		glEnable(GL_SCISSOR_TEST);
+	}
+	
 	glViewport(x, y, w, h);
 	glScissor (x, y, w, h);
 }
diff --git a/third_party/gldc/src/sh4.c b/third_party/gldc/src/sh4.c
index c535d6556..54e42c9b5 100644
--- a/third_party/gldc/src/sh4.c
+++ b/third_party/gldc/src/sh4.c
@@ -45,8 +45,8 @@ GL_FORCE_INLINE void _glPerspectiveDivideVertex(Vertex* vertex) {
     const float f = _glFastInvert(vertex->w);
 
     /* Convert to NDC and apply viewport */
-    vertex->xyz[0] = (vertex->xyz[0] * f *  320) + 320;
-    vertex->xyz[1] = (vertex->xyz[1] * f * -240) + 240;
+    vertex->xyz[0] = (vertex->xyz[0] * f * VIEWPORT.hwidth)  + VIEWPORT.x_plus_hwidth;
+    vertex->xyz[1] = (vertex->xyz[1] * f * VIEWPORT.hheight) + VIEWPORT.y_plus_hheight;
 
     /* Orthographic projections need to use invZ otherwise we lose
     the depth information. As w == 1, and clip-space range is -w to +w
diff --git a/third_party/gldc/src/state.c b/third_party/gldc/src/state.c
index 5b2332c22..5f6cd1400 100644
--- a/third_party/gldc/src/state.c
+++ b/third_party/gldc/src/state.c
@@ -253,20 +253,14 @@ void APIENTRY glGetIntegerv(GLenum pname, GLint *params) {
 }
 
 
-Viewport VIEWPORT = {
-    0, 0, 640, 480, 320.0f, 240.0f, 320.0f, 240.0f
-};
+Viewport VIEWPORT;
 
 /* Set the GL viewport */
 void APIENTRY glViewport(GLint x, GLint y, GLsizei width, GLsizei height) {
-    VIEWPORT.x = x;
-    VIEWPORT.y = y;
-    VIEWPORT.width   = width;
-    VIEWPORT.height  = height;
-    VIEWPORT.hwidth  = ((GLfloat) VIEWPORT.width) * 0.5f;
-    VIEWPORT.hheight = ((GLfloat) VIEWPORT.height) * 0.5f;
-    VIEWPORT.x_plus_hwidth  = VIEWPORT.x + VIEWPORT.hwidth;
-    VIEWPORT.y_plus_hheight = VIEWPORT.y + VIEWPORT.hheight;
+    VIEWPORT.hwidth  = ((GLfloat)width)  * 0.5f;
+    VIEWPORT.hheight = ((GLfloat)height) * -0.5f;
+    VIEWPORT.x_plus_hwidth  = x + VIEWPORT.hwidth;
+    VIEWPORT.y_plus_hheight = y + VIEWPORT.hheight;
 }