From 5f863016ca82b643b98f3759469e2f0b38f83485 Mon Sep 17 00:00:00 2001
From: Stephan Unverwerth <s.unverwerth@serenityos.org>
Date: Fri, 13 Aug 2021 01:06:26 +0200
Subject: [PATCH] LibGL: Implement glDepthMask

---
 Userland/Libraries/LibGL/GL/gl.h                |  2 ++
 Userland/Libraries/LibGL/GLContext.h            |  1 +
 Userland/Libraries/LibGL/GLUtils.cpp            |  5 +++++
 Userland/Libraries/LibGL/SoftwareGLContext.cpp  | 11 +++++++++++
 Userland/Libraries/LibGL/SoftwareGLContext.h    |  4 +++-
 Userland/Libraries/LibGL/SoftwareRasterizer.cpp |  4 +++-
 Userland/Libraries/LibGL/SoftwareRasterizer.h   |  1 +
 7 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/Userland/Libraries/LibGL/GL/gl.h b/Userland/Libraries/LibGL/GL/gl.h
index 7ccf501a636..8cf5b85155e 100644
--- a/Userland/Libraries/LibGL/GL/gl.h
+++ b/Userland/Libraries/LibGL/GL/gl.h
@@ -263,6 +263,7 @@ typedef char GLchar;
 typedef char GLbyte;
 typedef unsigned char GLuchar;
 typedef unsigned char GLubyte;
+typedef unsigned char GLboolean;
 typedef short GLshort;
 typedef unsigned short GLushort;
 typedef int GLint;
@@ -352,6 +353,7 @@ GLAPI void glTexParameterf(GLenum target, GLenum pname, GLfloat param);
 GLAPI void glBindTexture(GLenum target, GLuint texture);
 GLAPI void glActiveTexture(GLenum texture);
 GLAPI void glGetFloatv(GLenum pname, GLfloat* params);
+GLAPI void glDepthMask(GLboolean flag);
 
 #ifdef __cplusplus
 }
diff --git a/Userland/Libraries/LibGL/GLContext.h b/Userland/Libraries/LibGL/GLContext.h
index cf4966a4f01..f518e8ab478 100644
--- a/Userland/Libraries/LibGL/GLContext.h
+++ b/Userland/Libraries/LibGL/GLContext.h
@@ -63,6 +63,7 @@ public:
     virtual void gl_bind_texture(GLenum target, GLuint texture) = 0;
     virtual void gl_active_texture(GLenum texture) = 0;
     virtual void gl_get_floatv(GLenum pname, GLfloat* params) = 0;
+    virtual void gl_depth_mask(GLboolean flag) = 0;
 
     virtual void present() = 0;
 };
diff --git a/Userland/Libraries/LibGL/GLUtils.cpp b/Userland/Libraries/LibGL/GLUtils.cpp
index 732315fdd04..bdd374a4104 100644
--- a/Userland/Libraries/LibGL/GLUtils.cpp
+++ b/Userland/Libraries/LibGL/GLUtils.cpp
@@ -89,3 +89,8 @@ void glGetFloatv(GLenum pname, GLfloat* params)
 {
     g_gl_context->gl_get_floatv(pname, params);
 }
+
+void glDepthMask(GLboolean flag)
+{
+    g_gl_context->gl_depth_mask(flag);
+}
diff --git a/Userland/Libraries/LibGL/SoftwareGLContext.cpp b/Userland/Libraries/LibGL/SoftwareGLContext.cpp
index d1b5bc4c5d4..c50fece3343 100644
--- a/Userland/Libraries/LibGL/SoftwareGLContext.cpp
+++ b/Userland/Libraries/LibGL/SoftwareGLContext.cpp
@@ -1392,6 +1392,17 @@ void SoftwareGLContext::gl_get_floatv(GLenum pname, GLfloat* params)
     }
 }
 
+void SoftwareGLContext::gl_depth_mask(GLboolean flag)
+{
+    APPEND_TO_CALL_LIST_AND_RETURN_IF_NEEDED(gl_depth_mask, flag);
+
+    RETURN_WITH_ERROR_IF(m_in_draw_state, GL_INVALID_OPERATION);
+
+    auto options = m_rasterizer.options();
+    options.enable_depth_write = (flag != GL_FALSE);
+    m_rasterizer.set_options(options);
+}
+
 void SoftwareGLContext::present()
 {
     m_rasterizer.blit_to(*m_frontbuffer);
diff --git a/Userland/Libraries/LibGL/SoftwareGLContext.h b/Userland/Libraries/LibGL/SoftwareGLContext.h
index 4192fa8cde8..02dade49ed8 100644
--- a/Userland/Libraries/LibGL/SoftwareGLContext.h
+++ b/Userland/Libraries/LibGL/SoftwareGLContext.h
@@ -73,6 +73,7 @@ public:
     virtual void gl_bind_texture(GLenum target, GLuint texture) override;
     virtual void gl_active_texture(GLenum texture) override;
     virtual void gl_get_floatv(GLenum pname, GLfloat* params) override;
+    virtual void gl_depth_mask(GLboolean flag) override;
 
     virtual void present() override;
 
@@ -196,7 +197,8 @@ private:
             decltype(&SoftwareGLContext::gl_alpha_func),
             decltype(&SoftwareGLContext::gl_hint),
             decltype(&SoftwareGLContext::gl_read_buffer),
-            decltype(&SoftwareGLContext::gl_tex_parameter)>;
+            decltype(&SoftwareGLContext::gl_tex_parameter),
+            decltype(&SoftwareGLContext::gl_depth_mask)>;
 
         using ExtraSavedArguments = Variant<
             FloatMatrix4x4>;
diff --git a/Userland/Libraries/LibGL/SoftwareRasterizer.cpp b/Userland/Libraries/LibGL/SoftwareRasterizer.cpp
index a320a13ce41..61c17aa173f 100644
--- a/Userland/Libraries/LibGL/SoftwareRasterizer.cpp
+++ b/Userland/Libraries/LibGL/SoftwareRasterizer.cpp
@@ -265,7 +265,9 @@ static void rasterize_triangle(const RasterizerOptions& options, Gfx::Bitmap& re
                             continue;
                         }
 
-                        *depth = z;
+                        if (options.enable_depth_write)
+                            *depth = z;
+
                         z_pass_count++;
                     }
                 }
diff --git a/Userland/Libraries/LibGL/SoftwareRasterizer.h b/Userland/Libraries/LibGL/SoftwareRasterizer.h
index 19f7ce1c84f..6d4d15f2cf5 100644
--- a/Userland/Libraries/LibGL/SoftwareRasterizer.h
+++ b/Userland/Libraries/LibGL/SoftwareRasterizer.h
@@ -21,6 +21,7 @@ namespace GL {
 struct RasterizerOptions {
     bool shade_smooth { true };
     bool enable_depth_test { false };
+    bool enable_depth_write { true };
     bool enable_alpha_test { false };
     GLenum alpha_test_func { GL_ALWAYS };
     float alpha_test_ref_value { 0 };