From 79e150886a2bdcd24d06ccd7eef4c10a841d9cbe Mon Sep 17 00:00:00 2001
From: BearOso <bearoso@gmail.com>
Date: Fri, 31 Mar 2023 17:09:23 -0500
Subject: [PATCH] Add ability to force backdrop color for sprite extraction.

Only Gtk hotkey is hooked up so far.
---
 controls.cpp            | 21 +++++++++++++++++++++
 gfx.cpp                 |  1 +
 gtk/src/gtk_control.cpp |  2 +-
 gtk/src/snes9x.ui       |  4 ++--
 snes9x.h                |  1 +
 tileimpl.h              |  2 ++
 6 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/controls.cpp b/controls.cpp
index 878c809f..d31040fa 100644
--- a/controls.cpp
+++ b/controls.cpp
@@ -265,6 +265,7 @@ static const int	ptrspeeds[4] = { 1, 1, 4, 8 };
 	S(ToggleBG1), \
 	S(ToggleBG2), \
 	S(ToggleBG3), \
+	S(ToggleBackdrop), \
 	S(ToggleEmuTurbo), \
 	S(ToggleSprites), \
 	S(ToggleTransparency) \
@@ -2360,6 +2361,26 @@ void S9xApplyCommand (s9xcommand_t cmd, int16 data1, int16 data2)
 						S9xSetInfoString("All sound channels on");
 						break;
 
+					case ToggleBackdrop:
+						switch (Settings.ForcedBackdrop)
+						{
+						case 0:
+							Settings.ForcedBackdrop = 0xf81f;
+							break;
+						case 0xf81f:
+							Settings.ForcedBackdrop = 0x07e0;
+							break;
+						case 0x07e0:
+							Settings.ForcedBackdrop = 0x07ff;
+							break;
+						default:
+							Settings.ForcedBackdrop = 0;
+							break;
+						}
+						sprintf(buf, "Setting backdrop to 0x%04x", Settings.ForcedBackdrop);
+						S9xSetInfoString(buf);
+						break;
+
 					case ToggleBG0:
 						Settings.BG_Forced ^= 1;
 						DisplayStateChange("BG#0", !(Settings.BG_Forced & 1));
diff --git a/gfx.cpp b/gfx.cpp
index 6303aed2..fbeee33f 100644
--- a/gfx.cpp
+++ b/gfx.cpp
@@ -51,6 +51,7 @@ bool8 S9xGraphicsInit (void)
 
 	IPPU.OBJChanged = TRUE;
 	Settings.BG_Forced = 0;
+	Settings.ForcedBackdrop = 0;
 	S9xFixColourBrightness();
 	S9xBuildDirectColourMaps();
 
diff --git a/gtk/src/gtk_control.cpp b/gtk/src/gtk_control.cpp
index 259d1771..e2053a76 100644
--- a/gtk/src/gtk_control.cpp
+++ b/gtk/src/gtk_control.cpp
@@ -62,7 +62,7 @@ const BindingLink b_links[] =
         { "b_bg_layer_2",          "ToggleBG2"         },
         { "b_bg_layer_3",          "ToggleBG3"         },
         { "b_sprites",             "ToggleSprites"     },
-        { "b_bg_layering_hack",    "BGLayeringHack"    },
+        { "toggle_backdrop",       "ToggleBackdrop"    },
         { "b_screenshot",          "Screenshot"        },
         { "b_fullscreen",          "GTK_fullscreen"    },
         { "b_state_save_current",  "GTK_state_save_current" },
diff --git a/gtk/src/snes9x.ui b/gtk/src/snes9x.ui
index 98acdc08..f2896492 100644
--- a/gtk/src/snes9x.ui
+++ b/gtk/src/snes9x.ui
@@ -7198,7 +7198,7 @@
                                         <property name="visible">True</property>
                                         <property name="can_focus">False</property>
                                         <property name="xalign">0</property>
-                                        <property name="label" translatable="yes">BG layering hack</property>
+                                        <property name="label" translatable="yes">Toggle forced backdrop color</property>
                                       </object>
                                       <packing>
                                         <property name="top_attach">5</property>
@@ -7324,7 +7324,7 @@
                                       </packing>
                                     </child>
                                     <child>
-                                      <object class="GtkEntry" id="b_bg_layering_hack">
+                                      <object class="GtkEntry" id="toggle_backdrop">
                                         <property name="visible">True</property>
                                         <property name="can_focus">True</property>
                                         <property name="editable">False</property>
diff --git a/snes9x.h b/snes9x.h
index b52d8f83..502dbf98 100644
--- a/snes9x.h
+++ b/snes9x.h
@@ -247,6 +247,7 @@ struct SSettings
 	bool8	Transparency;
 	uint8	BG_Forced;
 	bool8	DisableGraphicWindows;
+	uint16  ForcedBackdrop;
 
 	bool8	DisplayTime;
 	bool8	DisplayFrameRate;
diff --git a/tileimpl.h b/tileimpl.h
index 9ea546e5..8b062354 100644
--- a/tileimpl.h
+++ b/tileimpl.h
@@ -481,6 +481,8 @@ namespace TileImpl {
 
 			GFX.RealScreenColors = IPPU.ScreenColors;
 			GFX.ScreenColors = GFX.ClipColors ? BlackColourMap : GFX.RealScreenColors;
+			if (Settings.ForcedBackdrop)
+				GFX.ScreenColors = &Settings.ForcedBackdrop;
 
 			OFFSET_IN_LINE;
 			for (l = GFX.StartY; l <= GFX.EndY; l++, Offset += GFX.PPL)