LibGL: Implement glGetTexImage

The plumbing was already there in LibGPU, so all that was left was to
implement the API :^)

Userland/Libraries/LibGL/GL/gl.h

@@ -739,6 +739,7 @@ GLAPI void glTexGenfv(GLenum coord, GLenum pname, GLfloat const* params);
 GLAPI void glTexGeni(GLenum coord, GLenum pname, GLint param);
 GLAPI void glRectf(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2);
 GLAPI void glRecti(GLint x1, GLint y1, GLint x2, GLint y2);
+GLAPI void glGetTexImage(GLenum target, GLint level, GLenum format, GLenum type, void* pixels);
 GLAPI void glGetTexLevelParameteriv(GLenum target, GLint level, GLenum pname, GLint* params);
 GLAPI void glPointSize(GLfloat size);
 GLAPI void glClipPlane(GLenum plane, GLdouble const* equation);

Userland/Libraries/LibGL/GLAPI.cpp

@@ -449,6 +449,11 @@ GLubyte const* glGetString(GLenum name)
     return g_gl_context->gl_get_string(name);
 }
 
+void glGetTexImage(GLenum target, GLint level, GLenum format, GLenum type, void* pixels)
+{
+    g_gl_context->gl_get_tex_image(target, level, format, type, pixels);
+}
+
 void glGetTexLevelParameteriv(GLenum target, GLint level, GLenum pname, GLint* params)
 {
     g_gl_context->gl_get_tex_parameter_integerv(target, level, pname, params);

Userland/Libraries/LibGL/GLContext.h

@@ -194,6 +194,7 @@ public:
     void gl_light_model(GLenum pname, GLfloat x, GLfloat y, GLfloat z, GLfloat w);
     void gl_bitmap(GLsizei width, GLsizei height, GLfloat xorig, GLfloat yorig, GLfloat xmove, GLfloat ymove, GLubyte const* bitmap);
     void gl_copy_tex_image_2d(GLenum target, GLint level, GLenum internalformat, GLint x, GLint y, GLsizei width, GLsizei height, GLint border);
+    void gl_get_tex_image(GLenum target, GLint level, GLenum format, GLenum type, void* pixels);
     void gl_get_tex_parameter_integerv(GLenum target, GLint level, GLenum pname, GLint* params);
     void gl_rect(GLdouble x1, GLdouble y1, GLdouble x2, GLdouble y2);
     void gl_tex_gen(GLenum coord, GLenum pname, GLint param);

Userland/Libraries/LibGL/Tex/Texture2D.cpp

@@ -11,6 +11,14 @@
 
 namespace GL {
 
+void Texture2D::download_texture_data(GLuint lod, GPU::ImageDataLayout output_layout, GLvoid* pixels)
+{
+    if (device_image().is_null())
+        return;
+
+    device_image()->read_texels(0, lod, { 0, 0, 0 }, pixels, output_layout);
+}
+
 void Texture2D::upload_texture_data(GLuint lod, GLenum internal_format, GPU::ImageDataLayout input_layout, GLvoid const* pixels)
 {
     // NOTE: Some target, format, and internal formats are currently unsupported.

Userland/Libraries/LibGL/Tex/Texture2D.h

@@ -27,6 +27,7 @@ public:
 
     virtual bool is_texture_2d() const override { return true; }
 
+    void download_texture_data(GLuint lod, GPU::ImageDataLayout output_layout, GLvoid* pixels);
     void upload_texture_data(GLuint lod, GLenum internal_format, GPU::ImageDataLayout input_layout, GLvoid const* pixels);
     void replace_sub_texture_data(GLuint lod, GPU::ImageDataLayout input_layout, Vector3<i32> const& output_offset, GLvoid const* pixels);
 

Userland/Libraries/LibGL/Texture.cpp

@@ -143,6 +143,36 @@ void GLContext::gl_gen_textures(GLsizei n, GLuint* textures)
     }
 }
 
+void GLContext::gl_get_tex_image(GLenum target, GLint level, GLenum format, GLenum type, void* pixels)
+{
+    RETURN_WITH_ERROR_IF(level < 0 || level > Texture2D::LOG2_MAX_TEXTURE_SIZE, GL_INVALID_VALUE);
+    auto pixel_type_or_error = get_validated_pixel_type(target, GL_NONE, format, type);
+    RETURN_WITH_ERROR_IF(pixel_type_or_error.is_error(), pixel_type_or_error.release_error().code());
+
+    auto texture_2d = m_active_texture_unit->texture_2d_target_texture();
+    VERIFY(!texture_2d.is_null());
+
+    u32 width = texture_2d->width_at_lod(level);
+    u32 height = texture_2d->height_at_lod(level);
+
+    GPU::ImageDataLayout output_layout = {
+        .pixel_type = pixel_type_or_error.release_value(),
+        .packing = get_packing_specification(PackingType::Pack),
+        .dimensions = {
+            .width = width,
+            .height = height,
+            .depth = 1,
+        },
+        .selection = {
+            .width = width,
+            .height = height,
+            .depth = 1,
+        },
+    };
+
+    texture_2d->download_texture_data(level, output_layout, pixels);
+}
+
 void GLContext::gl_get_tex_parameter_integerv(GLenum target, GLint level, GLenum pname, GLint* params)
 {
     RETURN_WITH_ERROR_IF(m_in_draw_state, GL_INVALID_OPERATION);