From 10e5065a5c72e9a704bac1500d92f41e5adb5751 Mon Sep 17 00:00:00 2001
From: ameerj <52414509+ameerj@users.noreply.github.com>
Date: Sun, 18 Jul 2021 23:59:31 -0400
Subject: gl_texture_cache: WIP texture rescale

---
 .../renderer_opengl/gl_texture_cache.cpp           | 70 +++++++++++++++++++++-
 src/video_core/renderer_opengl/gl_texture_cache.h  |  2 +
 2 files changed, 69 insertions(+), 3 deletions(-)

diff --git a/src/video_core/renderer_opengl/gl_texture_cache.cpp b/src/video_core/renderer_opengl/gl_texture_cache.cpp
index cdd352aef..9b2a09007 100644
--- a/src/video_core/renderer_opengl/gl_texture_cache.cpp
+++ b/src/video_core/renderer_opengl/gl_texture_cache.cpp
@@ -698,7 +698,10 @@ void Image::UploadMemory(const ImageBufferMap& map,
 void Image::DownloadMemory(ImageBufferMap& map,
                            std::span<const VideoCommon::BufferImageCopy> copies) {
     glMemoryBarrier(GL_PIXEL_BUFFER_BARRIER_BIT); // TODO: Move this to its own API
-
+    const bool is_rescaled = True(flags & ImageFlagBits::Rescaled);
+    if (is_rescaled) {
+        ScaleDown();
+    }
     glBindBuffer(GL_PIXEL_PACK_BUFFER, map.buffer);
     glPixelStorei(GL_PACK_ALIGNMENT, 1);
 
@@ -716,6 +719,9 @@ void Image::DownloadMemory(ImageBufferMap& map,
         }
         CopyImageToBuffer(copy, map.offset);
     }
+    if (is_rescaled) {
+        ScaleUp();
+    }
 }
 
 GLuint Image::StorageHandle() noexcept {
@@ -849,12 +855,70 @@ void Image::CopyImageToBuffer(const VideoCommon::BufferImageCopy& copy, size_t b
     }
 }
 
+void Image::Scale() {
+    // TODO: Pass scaling factor?
+    if (gl_format == 0 || gl_type == 0) {
+        // compressed textures
+        return;
+    }
+    if (info.type == ImageType::Linear) {
+        UNIMPLEMENTED();
+        return;
+    }
+    GLint prev_draw_fbo;
+    GLint prev_read_fbo;
+    glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &prev_draw_fbo);
+    glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, &prev_read_fbo);
+    const GLenum attachment = [this] {
+        switch (GetFormatType(info.format)) {
+        case SurfaceType::ColorTexture:
+            return GL_COLOR_ATTACHMENT0;
+        case SurfaceType::Depth:
+            return GL_DEPTH_ATTACHMENT;
+        case SurfaceType::DepthStencil:
+            return GL_DEPTH_STENCIL_ATTACHMENT;
+        default:
+            UNREACHABLE();
+            return GL_COLOR_ATTACHMENT0;
+        }
+    }();
+    const GLenum mask = [this] {
+        switch (GetFormatType(info.format)) {
+        case SurfaceType::ColorTexture:
+            return GL_COLOR_BUFFER_BIT;
+        case SurfaceType::Depth:
+            return GL_DEPTH_BUFFER_BIT;
+        case SurfaceType::DepthStencil:
+            return GL_STENCIL_BUFFER_BIT | GL_DEPTH_BUFFER_BIT;
+        default:
+            UNREACHABLE();
+            return GL_COLOR_BUFFER_BIT;
+        }
+    }();
+    const GLenum filter = (mask & GL_COLOR_BUFFER_BIT) != 0 ? GL_LINEAR : GL_NEAREST;
+    GLuint fbo_handle;
+    glGenFramebuffers(1, &fbo_handle);
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo_handle);
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, fbo_handle);
+    glNamedFramebufferTexture(fbo_handle, attachment, texture.handle, 0);
+
+    const size_t scaled_width = info.size.width;
+    const size_t scaled_height = info.size.height * 2;
+    glBlitNamedFramebuffer(fbo_handle, fbo_handle, 0, 0, info.size.width, info.size.height, 0, 0,
+                           scaled_width, scaled_height, mask, filter);
+    // TODO: resize texture?
+    glCopyTextureSubImage3D(texture.handle, 0, 0, 0, 0, 0, 0, scaled_width, scaled_height / 2);
+    // Restore previous framebuffers
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, prev_draw_fbo);
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, prev_read_fbo);
+}
+
 bool Image::ScaleUp() {
     if (True(flags & ImageFlagBits::Rescaled)) {
         return false;
     }
     flags |= ImageFlagBits::Rescaled;
-    UNIMPLEMENTED();
+    Scale();
     return true;
 }
 
@@ -863,7 +927,7 @@ bool Image::ScaleDown() {
         return false;
     }
     flags &= ~ImageFlagBits::Rescaled;
-    UNIMPLEMENTED();
+    Scale();
     return true;
 }
 
diff --git a/src/video_core/renderer_opengl/gl_texture_cache.h b/src/video_core/renderer_opengl/gl_texture_cache.h
index 58b36494b..324a0f1cb 100644
--- a/src/video_core/renderer_opengl/gl_texture_cache.h
+++ b/src/video_core/renderer_opengl/gl_texture_cache.h
@@ -198,6 +198,8 @@ private:
 
     void CopyImageToBuffer(const VideoCommon::BufferImageCopy& copy, size_t buffer_offset);
 
+    void Scale();
+
     OGLTexture texture;
     OGLTextureView store_view;
     GLenum gl_internal_format = GL_NONE;
-- 
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