Libretro cursorfix (#2822)

* [libretro] draw cursor directly to screen

This fixes some bugs where the cursor were not drawn in some games, and
also causing a cursor trail in other games.

* [libretro] Makes the cursor to start hidden

As many games don't use mouse, we keep it hidden while it was not moved.
Those wanting to take screenshots of the titlescreen don't risk taking a
screenshot of the cursor.

src/system/libretro/tic80_libretro.c

@@ -765,6 +765,49 @@ void tic80_libretro_update_mouse(tic80_mouse* mouse)
 	mouse->y = state->mouseY + TIC80_OFFSET_TOP;
 }
 
+/**
+ * Gets the 32-bit color value from the TIC-80 palette.
+ */
+static u32 get_screen_color(tic_mem* tic, u8 index)
+{
+	tic_rgb color = tic->ram->vram.palette.colors[index];
+	// The core requests RETRO_PIXEL_FORMAT_XRGB8888, so we format the color as 0x00RRGGBB.
+	return (color.r << 16) | (color.g << 8) | (color.b);
+}
+
+/**
+ * Draws a single pixel directly to the final screen buffer.
+ */
+static void draw_pixel_on_screen(u32* screen, s32 x, s32 y, u32 color)
+{
+	// Bounds check against the visible screen area
+	if (x < 0 || x >= TIC80_WIDTH || y < 0 || y >= TIC80_HEIGHT)
+		return;
+
+	s32 full_x = x + TIC80_OFFSET_LEFT;
+	s32 full_y = y + TIC80_OFFSET_TOP;
+
+	screen[full_y * TIC80_FULLWIDTH + full_x] = color;
+}
+
+/**
+ * Draws a horizontal line directly to the final screen buffer.
+ */
+static void draw_hline_on_screen(u32* screen, s32 x1, s32 x2, s32 y, u32 color)
+{
+	for (s32 x = x1; x <= x2; x++)
+		draw_pixel_on_screen(screen, x, y, color);
+}
+
+/**
+ * Draws a vertical line directly to the final screen buffer.
+ */
+static void draw_vline_on_screen(u32* screen, s32 x, s32 y1, s32 y2, u32 color)
+{
+	for (s32 y = y1; y <= y2; y++)
+		draw_pixel_on_screen(screen, x, y, color);
+}
+
 /**
  * Draws a software cursor on the screen where the mouse is.
  */
@@ -777,26 +820,45 @@ void tic80_libretro_mousecursor(tic80* game, tic80_mouse* mouse, enum mouse_curs
 		return;
 	}
 
-	tic_mem* tic = (tic_mem*)state->tic;
+	tic_mem* tic = (tic_mem*)game;
+	u32* screen = game->screen;
+	s32 mx = state->mouseX;
+	s32 my = state->mouseY;
 
-	// Draw the cursor.
-	// TODO: Fix the cursor not being drawn on the screen by possibly modifing game->screen directly.
+	// Calculate the final 32-bit color value
+	u32 cursor_color = get_screen_color(tic, state->mouseCursorColor);
+
+	// Draw the cursor directly to the screen buffer.
 	switch (cursortype) {
 		case MOUSE_CURSOR_NONE:
 			// Nothing.
 		break;
 		case MOUSE_CURSOR_DOT:
-			tic_api_pix(tic, state->mouseX, state->mouseY, state->mouseCursorColor, false);
+			draw_pixel_on_screen(screen, mx, my, cursor_color);
 		break;
 		case MOUSE_CURSOR_CROSS:
-			tic_api_line(tic, state->mouseX - 4, state->mouseY, state->mouseX - 2, state->mouseY, state->mouseCursorColor);
-			tic_api_line(tic, state->mouseX + 2, state->mouseY, state->mouseX + 4, state->mouseY, state->mouseCursorColor);
-			tic_api_line(tic, state->mouseX, state->mouseY - 4, state->mouseX, state->mouseY - 2, state->mouseCursorColor);
-			tic_api_line(tic, state->mouseX, state->mouseY + 2, state->mouseX, state->mouseY + 4, state->mouseCursorColor);
+			draw_hline_on_screen(screen, mx - 4, mx - 2, my, cursor_color);
+			draw_hline_on_screen(screen, mx + 2, mx + 4, my, cursor_color);
+			draw_vline_on_screen(screen, mx, my - 4, my - 2, cursor_color);
+			draw_vline_on_screen(screen, mx, my + 2, my + 4, cursor_color);
 		break;
 		case MOUSE_CURSOR_ARROW:
-			tic_api_tri(tic, state->mouseX, state->mouseY, state->mouseX + 3, state->mouseY, state->mouseX, state->mouseY + 3, state->mouseCursorColor);
-			tic_api_line(tic, state->mouseX + 3, state->mouseY, state->mouseX, state->mouseY + 3, tic_color_black);
+		{
+			// Calculate black for the outline.
+			u32 black_color = get_screen_color(tic, tic_color_black);
+
+			// Draw the filled triangle part of the arrow
+			for (int y = 0; y <= 2; y++) {
+				for (int x = 0; x <= 2 - y; x++) {
+					draw_pixel_on_screen(screen, mx + x, my + y, cursor_color);
+				}
+			}
+			// Draw the black outline (hypotenuse of the triangle)
+			draw_pixel_on_screen(screen, mx + 3, my, black_color);
+			draw_pixel_on_screen(screen, mx + 2, my + 1, black_color);
+			draw_pixel_on_screen(screen, mx + 1, my + 2, black_color);
+			draw_pixel_on_screen(screen, mx, my + 3, black_color);
+		}
 		break;
 	}
 }
@@ -972,7 +1034,7 @@ void tic80_libretro_variables(bool startup)
 		state->mouseHideTimerStart = atoi(var.value);
 		if (state->mouseHideTimerStart > 0) {
 			state->mouseHideTimerStart = state->mouseHideTimerStart * TIC80_FRAMERATE;
-			state->mouseHideTimer = state->mouseHideTimerStart;
+			state->mouseHideTimer = 0; // Cursor starts hidden
 		}
 		else {
 			state->mouseHideTimerStart = 0;