LibGL: Implement glBindTexture()

Textures are now initialized with a nullptr upon generation.
They are only actually created once they are bound to a target.
Currently only the GL_TEXTURE_2D target is supported.
The software rasterizer now allows rendering with or without
a bound TEXTURE_2D.

Userland/Applications/3DFileViewer/main.cpp

@@ -153,6 +153,7 @@ bool GLContextWidget::load(const String& filename)
     glGenTextures(1, &tex);
     if (texture_image) {
         // Upload texture data to the GL
+        glBindTexture(GL_TEXTURE_2D, tex);
         glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, texture_image->width(), texture_image->height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, texture_image->scanline(0));
     } else {
         dbgln("3DFileViewer: Couldn't load texture for {}", filename);

Userland/Libraries/LibGL/GL/gl.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ * Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -257,6 +258,7 @@ GLAPI void glReadBuffer(GLenum mode);
 GLAPI void glReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid* pixels);
 GLAPI void glTexImage2D(GLenum target, GLint level, GLint internalFormat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, const GLvoid* data);
 GLAPI void glTexCoord2f(GLfloat s, GLfloat t);
+GLAPI void glBindTexture(GLenum target, GLuint texture);
 
 #ifdef __cplusplus
 }

Userland/Libraries/LibGL/GLContext.h

@@ -59,6 +59,7 @@ public:
     virtual void gl_read_pixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid* pixels) = 0;
     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_coord(GLfloat s, GLfloat t, GLfloat r, GLfloat q) = 0;
+    virtual void gl_bind_texture(GLenum target, GLuint texture) = 0;
 
     virtual void present() = 0;
 };

Userland/Libraries/LibGL/GLTexture.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ * Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -23,3 +24,8 @@ void glTexImage2D(GLenum target, GLint level, GLint internalFormat, GLsizei widt
 {
     g_gl_context->gl_tex_image_2d(target, level, internalFormat, width, height, border, format, type, data);
 }
+
+void glBindTexture(GLenum target, GLuint texture)
+{
+    g_gl_context->gl_bind_texture(target, texture);
+}

Userland/Libraries/LibGL/SoftwareGLContext.cpp

@@ -313,7 +313,12 @@ void SoftwareGLContext::gl_end()
         }
 
         // FIXME: Change this when we have texture units/multi-texturing
-        m_rasterizer.submit_triangle(triangle, *static_ptr_cast<Texture2D>(m_allocated_textures.find(1)->value));
+        if (m_bound_texture_2d == 0) {
+            m_rasterizer.submit_triangle(triangle);
+        } else {
+            auto it = m_allocated_textures.find(m_bound_texture_2d);
+            m_rasterizer.submit_triangle(triangle, *static_ptr_cast<Texture2D>(it->value));
+        }
     }
 
     triangle_list.clear();
@@ -663,11 +668,11 @@ void SoftwareGLContext::gl_gen_textures(GLsizei n, GLuint* textures)
 
     m_name_allocator.allocate(n, textures);
 
-    // Let's allocate a new texture for each texture name
+    // Initialize all texture names with a nullptr
     for (auto i = 0; i < n; i++) {
         GLuint name = textures[i];
 
-        m_allocated_textures.set(name, adopt_ref(*new Texture2D()));
+        m_allocated_textures.set(name, nullptr);
     }
 }
 
@@ -678,10 +683,13 @@ void SoftwareGLContext::gl_delete_textures(GLsizei n, const GLuint* textures)
 
     m_name_allocator.free(n, textures);
 
-    // Let's allocate a new texture for each texture name
     for (auto i = 0; i < n; i++) {
         GLuint name = textures[i];
 
+        // unbind texture if it is currently bound
+        if (m_bound_texture_2d == name)
+            m_bound_texture_2d = 0;
+
         m_allocated_textures.remove(name);
     }
 }
@@ -693,6 +701,9 @@ void SoftwareGLContext::gl_tex_image_2d(GLenum target, GLint level, GLint intern
     // We only support GL_TEXTURE_2D for now
     RETURN_WITH_ERROR_IF(target != GL_TEXTURE_2D, GL_INVALID_ENUM);
 
+    // Check if there is actually a texture bound
+    RETURN_WITH_ERROR_IF(target == GL_TEXTURE_2D && m_bound_texture_2d == 0, GL_INVALID_OPERATION);
+
     // We only support symbolic constants for now
     RETURN_WITH_ERROR_IF(!(internal_format == GL_RGB || internal_format == GL_RGBA), GL_INVALID_ENUM);
     RETURN_WITH_ERROR_IF(type != GL_UNSIGNED_BYTE, GL_INVALID_VALUE);
@@ -1226,6 +1237,55 @@ void SoftwareGLContext::gl_read_pixels(GLint x, GLint y, GLsizei width, GLsizei
     }
 }
 
+void SoftwareGLContext::gl_bind_texture(GLenum target, GLuint texture)
+{
+    RETURN_WITH_ERROR_IF(m_in_draw_state, GL_INVALID_OPERATION);
+    // FIXME: We only support GL_TEXTURE_2D for now
+    RETURN_WITH_ERROR_IF(target != GL_TEXTURE_2D, GL_INVALID_ENUM);
+
+    if (texture == 0) {
+        switch (target) {
+        case GL_TEXTURE_2D:
+            m_bound_texture_2d = 0;
+            return;
+        default:
+            VERIFY_NOT_REACHED();
+            return;
+        }
+    }
+
+    auto it = m_allocated_textures.find(texture);
+
+    // The texture name does not exist
+    RETURN_WITH_ERROR_IF(it == m_allocated_textures.end(), GL_INVALID_VALUE);
+
+    auto texture_object = it->value;
+
+    // Binding a texture to a different target than it was first bound is an invalid operation
+    // FIXME: We only support GL_TEXTURE_2D for now
+    RETURN_WITH_ERROR_IF(target == GL_TEXTURE_2D && !texture_object.is_null() && !texture_object->is_texture_2d(), GL_INVALID_OPERATION);
+
+    if (!texture_object) {
+        // This is the first time the texture is bound. Allocate an actual texture object
+        switch (target) {
+        case GL_TEXTURE_2D:
+            texture_object = adopt_ref(*new Texture2D());
+            break;
+        default:
+            VERIFY_NOT_REACHED();
+            break;
+        }
+
+        m_allocated_textures.set(texture, texture_object);
+    }
+
+    switch (target) {
+    case GL_TEXTURE_2D:
+        m_bound_texture_2d = texture;
+        break;
+    }
+}
+
 void SoftwareGLContext::present()
 {
     m_rasterizer.blit_to(*m_frontbuffer);

Userland/Libraries/LibGL/SoftwareGLContext.h

@@ -68,6 +68,7 @@ public:
     virtual void gl_read_pixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid* pixels) override;
     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_coord(GLfloat s, GLfloat t, GLfloat r, GLfloat q) override;
+    virtual void gl_bind_texture(GLenum target, GLuint texture) override;
 
     virtual void present() override;
 
@@ -128,6 +129,8 @@ private:
 
     GLenum m_current_read_buffer = GL_BACK;
 
+    GLuint m_bound_texture_2d = 0;
+
     NonnullRefPtr<Gfx::Bitmap> m_frontbuffer;
 
     Clipper m_clipper;

Userland/Libraries/LibGL/SoftwareRasterizer.cpp

@@ -414,6 +414,13 @@ SoftwareRasterizer::SoftwareRasterizer(const Gfx::IntSize& min_size)
 {
 }
 
+void SoftwareRasterizer::submit_triangle(const GLTriangle& triangle)
+{
+    rasterize_triangle(m_options, *m_render_target, *m_depth_buffer, triangle, [](const FloatVector2&, const FloatVector4& color) -> FloatVector4 {
+        return color;
+    });
+}
+
 void SoftwareRasterizer::submit_triangle(const GLTriangle& triangle, const Texture2D& texture)
 {
     rasterize_triangle(m_options, *m_render_target, *m_depth_buffer, triangle, [&texture](const FloatVector2& uv, const FloatVector4& color) -> FloatVector4 {

Userland/Libraries/LibGL/SoftwareRasterizer.h

@@ -32,6 +32,7 @@ public:
     SoftwareRasterizer(const Gfx::IntSize& min_size);
 
     void submit_triangle(const GLTriangle& triangle, const Texture2D& texture);
+    void submit_triangle(const GLTriangle& triangle);
     void resize(const Gfx::IntSize& min_size);
     void clear_color(const FloatVector4&);
     void clear_depth(float);