Add support for two different inverse modes

- Inverse mode invert (default) will invert the color in shader.
- Inverse mode swap will simply swap the foreground and background
  colors. This is the default behavior of libtsm and GodotXterm v3.

addons/godot_xterm/native/src/terminal.cpp

@@ -31,6 +31,14 @@ void Terminal::_bind_methods()
 	ClassDB::bind_method(D_METHOD("set_max_scrollback", "max_scrollback"), &Terminal::set_max_scrollback);
 	ClassDB::add_property("Terminal", PropertyInfo(Variant::INT, "max_scrollback"), "set_max_scrollback", "get_max_scrollback");
 
+	// Inverse mode.
+
+	BIND_ENUM_CONSTANT(INVERSE_MODE_INVERT);
+	BIND_ENUM_CONSTANT(INVERSE_MODE_SWAP);
+	ClassDB::bind_method(D_METHOD("get_inverse_mode"), &Terminal::get_inverse_mode);
+	ClassDB::bind_method(D_METHOD("set_inverse_mode", "inverse_mode"), &Terminal::set_inverse_mode);
+	ClassDB::add_property("Terminal", PropertyInfo(Variant::INT, "inverse_mode", PROPERTY_HINT_ENUM, "Invert,Swap"), "set_inverse_mode", "get_inverse_mode");
+
 	// Blink.
 
 	ClassDB::add_property_group("Terminal", "Blink", "blink_");
@@ -53,6 +61,8 @@ Terminal::Terminal()
 	blink_on_time = 0.6;
 	blink_off_time = 0.3;
 
+	inverse_mode = InverseMode::INVERSE_MODE_INVERT;
+
 	if (tsm_screen_new(&screen, NULL, NULL))
 	{
 		ERR_PRINT("Failed to create tsm screen.");
@@ -199,6 +209,9 @@ int Terminal::_draw_cb(struct tsm_screen *con,
 		? term->palette[attr->bccode]
 		: Color(attr->br / 255.0f, attr->bg / 255.0f, attr->bb / 255.0f);
 
+	if (attr->inverse && term->inverse_mode == InverseMode::INVERSE_MODE_SWAP)
+		std::swap(fgcol, bgcol);
+
 	// Draw background.
 	term->back_image->set_pixel(posx, posy, bgcol);
 
@@ -491,3 +504,17 @@ float Terminal::get_blink_off_time() const
 {
 	return blink_off_time;
 }
+
+void Terminal::set_inverse_mode(const int mode) {
+	inverse_mode = static_cast<InverseMode>(mode);
+
+	bool inverse_enabled = inverse_mode == InverseMode::INVERSE_MODE_INVERT;
+	back_material->set_shader_parameter("inverse_enabled", inverse_enabled);
+	fore_material->set_shader_parameter("inverse_enabled", inverse_enabled);
+
+	refresh();
+}
+
+int Terminal::get_inverse_mode() const {
+	return static_cast<int>(inverse_mode);
+}

addons/godot_xterm/native/src/terminal.h

@@ -34,6 +34,11 @@ namespace godot
       BLINK = 1 << 1,
     };
 
+    enum InverseMode {
+      INVERSE_MODE_INVERT,
+      INVERSE_MODE_SWAP,
+    };
+
     Terminal();
     ~Terminal();
 
@@ -52,6 +57,9 @@ namespace godot
     void set_blink_off_time(const float p_blink_off_time);
     float get_blink_off_time() const;
 
+    void set_inverse_mode(const int mode);
+    int get_inverse_mode() const;
+
     void write(Variant data);
 
   protected:
@@ -66,6 +74,8 @@ namespace godot
     float blink_on_time;
     float blink_off_time;
 
+    InverseMode inverse_mode;
+
     RenderingServer *rs;
 
     tsm_screen *screen;
@@ -118,3 +128,5 @@ namespace godot
   };
 
 } // namespace godot
+
+VARIANT_ENUM_CAST(Terminal::InverseMode);

addons/godot_xterm/shaders/common.gdshaderinc

@@ -13,6 +13,7 @@ uniform vec2 cell_size;
 uniform vec2 grid_size;
 
 uniform sampler2D attributes;
+uniform bool inverse_enabled = true;
 
 #ifdef BACKGROUND
 uniform vec4 background_color;
@@ -46,7 +47,7 @@ void fragment() {
 		color = texture(TEXTURE, UV);
 #endif
 
-		if (has_attribute(sample_uv, FLAG_INVERSE)) {
+		if (has_attribute(sample_uv, FLAG_INVERSE) && inverse_enabled) {
 			color = vec4(1.0 - color.rgb, color.a);
 		}