graphics: address performance regression with Image Resize (#504)

## Link to GitHub Issue, if one exists
Regressed by #401 

## Description of change
Two things from testing SDVX Live2D -

1. ColorFill is almost always too expensive and will lead to drops
1. Scale factor of 0.5 causes GPU to sync and causes drops

(ARGB/XRGB doesn't matter, linear filtering doesn't matter)

1 is fixed by removing ColorFill calls on every frame - instead only do
this once when the user changes the duplicate option (on the next frame)

2 is fixed by updating the UI (limit the slider) though people can
ctrl+click to override these slider limits.

The warning label will be kept with slightly reworded text.

## Testing
tested in sdvx eg final (sudden death) - on my RTX 4070, my FPS is rock
solid 120 fps even with image resize on now.

src/spice2x/cfg/screen_resize.cpp

@@ -81,18 +81,7 @@ namespace cfg {
         
         load_bool_value(doc, root + "enable_screen_resize", this->enable_screen_resize);
         if (this->enable_screen_resize) {
-            if (avs::game::is_model("KFC")) {
-                log_warning(
-                    "ScreenResize",
-                    "Image Resize feature enabled for SDVX; enabling this is known to significantly "
-                    "lower framerate for songs with Live2D!");
-                deferredlogs::defer_error_messages({
-                    "Image Resize + SDVX Live2D performance warning",
-                    "    Enabling Image Resize feature is known to have significant impact",
-                    "    on Live2D performance; you should disable it"});
-            } else {
-                log_misc("ScreenResize", "enabled by config file");
-            }
+            log_misc("ScreenResize", "enabled by config file");
         }
 
         load_bool_value(doc, root + "enable_linear_filter", this->enable_linear_filter);

src/spice2x/cfg/screen_resize.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <atomic>
 #include <memory>
 #include <string>
 #include <optional>
@@ -51,6 +52,9 @@ namespace cfg {
         bool enable_linear_filter = true;
         fullscreen_setting scene_settings[4];
 
+        // state
+        std::atomic<bool> need_surface_clean = false;
+
         // windowed mode sizing
         // Windows terminology:
         //     window = rectangle including the frame

src/spice2x/hooks/graphics/backends/d3d9/d3d9_device.cpp

@@ -742,14 +742,12 @@ void SurfaceHook(IDirect3DDevice9 *pReal) {
     const int w = param.BackBufferWidth;
     const int h = param.BackBufferHeight;
 
-    if (cfg::SCREENRESIZE->enable_screen_resize) {
-        RECT rect {
-            0,
-            0,
-            (LONG)topSurface_width,
-            (LONG)topSurface_height,
-        };
-        pReal->ColorFill(topSurface, &rect, D3DCOLOR_XRGB(0, 0, 0));
+    // this code used to clear the surface using ColorFill on every call, but
+    // this turned out to be very expensive, leading to major frame drops in
+    // SDVX Live2D scenario
+    if (cfg::SCREENRESIZE->need_surface_clean) {
+        pReal->ColorFill(topSurface, nullptr, D3DCOLOR_XRGB(0, 0, 0));
+        cfg::SCREENRESIZE->need_surface_clean = false;
     }
     
     D3DLOCKED_RECT rect;

src/spice2x/overlay/windows/screen_resize.cpp

@@ -103,12 +103,16 @@ namespace overlay::windows {
 
         if (avs::game::is_model("KFC")) {
             ImGui::TextColored(ImVec4(1, 0.5f, 0.5f, 1.f),
-                "Warning: Enabling Image Resize will significantly\n"
-                "lower framerate for songs with Live2D!");
+                "Warning: Enabling Image Resize uses more GPU\n"
+                "resources and may significantly lower framerate\n"
+                "for songs with Live2D! Results may vary, use at\n"
+                "your own risk.");
         } else {
             ImGui::TextColored(ImVec4(1, 0.5f, 0.5f, 1.f),
-                "Warning: Some games are known to have significant\n"
-                "performance issues when Image Resize is enabled.");
+                "Warning: Enabling Image Resize uses more GPU\n"
+                "resources and may significantly lower framerate\n"
+                "in some situations! Results may vary, use at\n"
+                "your own risk.");
         }
 
         // enable checkbox
@@ -152,22 +156,27 @@ namespace overlay::windows {
         // aspect ratio
         ImGui::Checkbox("Keep Aspect Ratio", &scene.keep_aspect_ratio);
         if (scene.keep_aspect_ratio) {
-            if (ImGui::SliderFloat("Scale", &scene.scale_x, 0.5f, 2.5f)) {
+
+            // we want to avoid zooming out below 0.6 as it will cause StretchRect calls to
+            // go on a slow sync path with the GPU, leading to frame drops in some situations
+            // (e.g., SDVX Live2D)
+
+            if (ImGui::SliderFloat("Scale", &scene.scale_x, 0.6f, 2.5f)) {
                 scene.scale_y = scene.scale_x;
             }
             ImGui::SameLine();
             ImGui::HelpMarker("Hint: ctrl + click on the slider to type in a numeric value.");
         } else {
-            ImGui::SliderFloat("Width Scale", &scene.scale_x, 0.5f, 2.5f);
+            ImGui::SliderFloat("Width Scale", &scene.scale_x, 0.6f, 2.5f);
             ImGui::SameLine();
             ImGui::HelpMarker("Hint: ctrl + click on the slider to type in a numeric value.");
-            ImGui::SliderFloat("Height Scale", &scene.scale_y, 0.5f, 2.5f);
+            ImGui::SliderFloat("Height Scale", &scene.scale_y, 0.6f, 2.5f);
             ImGui::SameLine();
             ImGui::HelpMarker("Hint: ctrl + click on the slider to type in a numeric value.");
         }
 
         static const char* dupe_items[] = { "None", "Copy Left", "Copy Right" };
-        ImGui::Combo(
+        const bool duplicate_changed = ImGui::Combo(
             "Duplicate",
             reinterpret_cast<int *>(&scene.duplicate),
             dupe_items,
@@ -178,6 +187,11 @@ namespace overlay::windows {
             "wrap-around effect when an offset is set.");
 
         ImGui::EndDisabled();
+
+        // tell d3d9 device to clear surface to get rid of ghost image
+        if (duplicate_changed) {
+            cfg::SCREENRESIZE->need_surface_clean = true;
+        }
     }
 
     void ScreenResize::build_windowed_config() {