LibGL: Implement glTexEnvf

This controls how fetched texels are combined with the color that was
produced by a preceding texture unit or with the vertex color if it is
the first texture unit.

Currently only a small subset of possible combine modes is implemented
as required by glquake.

7 files changed, 66 insertions, 7 deletions

diff --git a/Userland/Libraries/LibGL/GL/gl.h b/Userland/Libraries/LibGL/GL/gl.h
index bc9654e54b..a1acd0c044 100644
--- a/Userland/Libraries/LibGL/GL/gl.h
+++ b/Userland/Libraries/LibGL/GL/gl.h
@@ -358,6 +358,7 @@ GLAPI void glTexCoord2f(GLfloat s, GLfloat t);
 GLAPI void glTexCoord4fv(const GLfloat* v);
 GLAPI void glTexParameteri(GLenum target, GLenum pname, GLint param);
 GLAPI void glTexParameterf(GLenum target, GLenum pname, GLfloat param);
+GLAPI void glTexEnvf(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);
diff --git a/Userland/Libraries/LibGL/GLContext.h b/Userland/Libraries/LibGL/GLContext.h
index b1e869fab0..6dd6f37a16 100644
--- a/Userland/Libraries/LibGL/GLContext.h
+++ b/Userland/Libraries/LibGL/GLContext.h
@@ -60,6 +60,7 @@ public:
     virtual void gl_tex_image_2d(GLenum target, GLint level, GLint internal_format, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, const GLvoid* data) = 0;
     virtual void gl_tex_parameter(GLenum target, GLenum pname, GLfloat param) = 0;
     virtual void gl_tex_coord(GLfloat s, GLfloat t, GLfloat r, GLfloat q) = 0;
+    virtual void gl_tex_env(GLenum target, GLenum pname, GLfloat param) = 0;
     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;
diff --git a/Userland/Libraries/LibGL/GLTexture.cpp b/Userland/Libraries/LibGL/GLTexture.cpp
index 97364df1bf..03e86d9d6b 100644
--- a/Userland/Libraries/LibGL/GLTexture.cpp
+++ b/Userland/Libraries/LibGL/GLTexture.cpp
@@ -46,3 +46,8 @@ void glTexParameterf(GLenum target, GLenum pname, GLfloat param)
 {
     g_gl_context->gl_tex_parameter(target, pname, param);
 }
+
+void glTexEnvf(GLenum target, GLenum pname, GLfloat param)
+{
+    g_gl_context->gl_tex_env(target, pname, param);
+}
diff --git a/Userland/Libraries/LibGL/SoftwareGLContext.cpp b/Userland/Libraries/LibGL/SoftwareGLContext.cpp
index 0cc5f507a0..e068bb0edd 100644
--- a/Userland/Libraries/LibGL/SoftwareGLContext.cpp
+++ b/Userland/Libraries/LibGL/SoftwareGLContext.cpp
@@ -1482,6 +1482,36 @@ void SoftwareGLContext::gl_tex_coord_pointer(GLint size, GLenum type, GLsizei st
     m_client_tex_coord_pointer.pointer = pointer;
 }
 
+void SoftwareGLContext::gl_tex_env(GLenum target, GLenum pname, GLfloat param)
+{
+    APPEND_TO_CALL_LIST_AND_RETURN_IF_NEEDED(gl_tex_env, target, pname, param);
+    RETURN_WITH_ERROR_IF(m_in_draw_state, GL_INVALID_OPERATION);
+
+    if (target == GL_TEXTURE_ENV) {
+        if (pname == GL_TEXTURE_ENV_MODE) {
+            auto param_enum = static_cast<GLenum>(param);
+
+            switch (param_enum) {
+            case GL_MODULATE:
+            case GL_REPLACE:
+            case GL_DECAL:
+                m_active_texture_unit->set_env_mode(param_enum);
+                break;
+            default:
+                // FIXME: We currently only support a subset of possible param values. Implement the rest!
+                RETURN_WITH_ERROR_IF(true, GL_INVALID_ENUM);
+                break;
+            }
+        } else {
+            // FIXME: We currently only support a subset of possible pname values. Implement the rest!
+            RETURN_WITH_ERROR_IF(true, GL_INVALID_ENUM);
+        }
+    } else {
+        // FIXME: We currently only support a subset of possible target values. Implement the rest!
+        RETURN_WITH_ERROR_IF(true, GL_INVALID_ENUM);
+    }
+}
+
 void SoftwareGLContext::gl_draw_arrays(GLenum mode, GLint first, GLsizei count)
 {
     APPEND_TO_CALL_LIST_AND_RETURN_IF_NEEDED(gl_draw_arrays, mode, first, count);
diff --git a/Userland/Libraries/LibGL/SoftwareGLContext.h b/Userland/Libraries/LibGL/SoftwareGLContext.h
index 23ad3e2db9..92fa1242f8 100644
--- a/Userland/Libraries/LibGL/SoftwareGLContext.h
+++ b/Userland/Libraries/LibGL/SoftwareGLContext.h
@@ -70,6 +70,7 @@ public:
     virtual void gl_tex_image_2d(GLenum target, GLint level, GLint internal_format, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, const GLvoid* data) override;
     virtual void gl_tex_parameter(GLenum target, GLenum pname, GLfloat param) override;
     virtual void gl_tex_coord(GLfloat s, GLfloat t, GLfloat r, GLfloat q) override;
+    virtual void gl_tex_env(GLenum target, GLenum pname, GLfloat param) override;
     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;
diff --git a/Userland/Libraries/LibGL/SoftwareRasterizer.cpp b/Userland/Libraries/LibGL/SoftwareRasterizer.cpp
index cfd5513476..9c5341f517 100644
--- a/Userland/Libraries/LibGL/SoftwareRasterizer.cpp
+++ b/Userland/Libraries/LibGL/SoftwareRasterizer.cpp
@@ -483,9 +483,7 @@ SoftwareRasterizer::SoftwareRasterizer(const Gfx::IntSize& min_size)
 void SoftwareRasterizer::submit_triangle(const GLTriangle& triangle, const Array<TextureUnit, 32>& texture_units)
 {
     rasterize_triangle(m_options, *m_render_target, *m_depth_buffer, triangle, [this, &texture_units](const FloatVector2& uv, const FloatVector4& color, float z) -> FloatVector4 {
-        // TODO: We'd do some kind of multitexturing/blending here
-        // Construct a vector for the texel we want to sample
-        FloatVector4 texel = color;
+        FloatVector4 fragment = color;
 
         for (const auto& texture_unit : texture_units) {
 
@@ -493,8 +491,27 @@ void SoftwareRasterizer::submit_triangle(const GLTriangle& triangle, const Array
             if (!texture_unit.is_bound())
                 continue;
 
-            // FIXME: Don't assume Texture2D, _and_ work out how we blend/do multitexturing properly.....
-            texel = texel * static_ptr_cast<Texture2D>(texture_unit.bound_texture())->sampler().sample(uv);
+            // FIXME: Don't assume Texture2D
+            auto texel = texture_unit.bound_texture_2d()->sampler().sample(uv);
+
+            // FIXME: Implement more blend modes
+            switch (texture_unit.env_mode()) {
+            case GL_MODULATE:
+            default:
+                fragment = fragment * texel;
+                break;
+            case GL_REPLACE:
+                fragment = texel;
+                break;
+            case GL_DECAL: {
+                float src_alpha = fragment.w();
+                float one_minus_src_alpha = 1 - src_alpha;
+                fragment.set_x(texel.x() * src_alpha + fragment.x() * one_minus_src_alpha);
+                fragment.set_y(texel.y() * src_alpha + fragment.y() * one_minus_src_alpha);
+                fragment.set_z(texel.z() * src_alpha + fragment.z() * one_minus_src_alpha);
+                break;
+            }
+            }
         }
 
         // Calculate fog
@@ -516,10 +533,10 @@ void SoftwareRasterizer::submit_triangle(const GLTriangle& triangle, const Array
             }
 
             // Mix texel with fog
-            texel = mix(m_options.fog_color, texel, factor);
+            fragment = mix(m_options.fog_color, fragment, factor);
         }
 
-        return texel;
+        return fragment;
     });
 }
 
diff --git a/Userland/Libraries/LibGL/Tex/TextureUnit.h b/Userland/Libraries/LibGL/Tex/TextureUnit.h
index d54341d194..2433012515 100644
--- a/Userland/Libraries/LibGL/Tex/TextureUnit.h
+++ b/Userland/Libraries/LibGL/Tex/TextureUnit.h
@@ -24,10 +24,14 @@ public:
     GLenum currently_bound_target() const { return m_currently_bound_target; }
     bool is_bound() const { return !m_currently_bound_texture.is_null(); }
 
+    void set_env_mode(GLenum mode) { m_env_mode = mode; }
+    GLenum env_mode() const { return m_env_mode; }
+
 private:
     mutable RefPtr<Texture2D> m_texture_target_2d { nullptr };
     mutable RefPtr<Texture> m_currently_bound_texture { nullptr };
     GLenum m_currently_bound_target;
+    GLenum m_env_mode { GL_MODULATE };
 };
 
 }