From b5927ba9a22dd256603b81d452fdb3cfaf0dc2ba Mon Sep 17 00:00:00 2001
From: kdx <kikoodx@paranoici.org>
Date: Wed, 29 Nov 2023 11:24:04 +0100
Subject: interlace effect

---
 headers/TZR.h           |  1 +
 headers/TZR_globals.h   |  1 +
 headers/TZR_types.h     |  1 +
 sources/TZR_DrawBegin.c |  5 +++++
 sources/TZR_DrawEnd.c   | 18 ++++++++++++++++++
 sources/TZR_Init.c      |  8 ++++++++
 sources/TZR_Quit.c      |  4 ++++
 sources/globals.c       |  1 +
 8 files changed, 39 insertions(+)

diff --git a/headers/TZR.h b/headers/TZR.h
index 7d55471..17129c8 100644
--- a/headers/TZR.h
+++ b/headers/TZR.h
@@ -17,6 +17,7 @@
 	.target_fps=60, \
 	.ratio=1.0f, \
 	.pixel_perfect=true, \
+	.interlace=false, \
 	.hd_render=false, \
 	.scale_linear=false, \
 	.show_cursor=false, \
diff --git a/headers/TZR_globals.h b/headers/TZR_globals.h
index 208ad0b..6c4bd04 100644
--- a/headers/TZR_globals.h
+++ b/headers/TZR_globals.h
@@ -12,6 +12,7 @@ extern size_t ___tzr_resources_size;
 extern SDL_Window *___tzr_window;
 extern SDL_Renderer *___tzr_renderer;
 extern SDL_Texture *___tzr_target;
+extern SDL_Texture *___tzr_target_pre;
 extern unsigned long ___tzr_tick;
 extern unsigned long ___tzr_next_time;
 extern unsigned long ___tzr_min_dt;
diff --git a/headers/TZR_types.h b/headers/TZR_types.h
index cd0baad..e7d13fc 100644
--- a/headers/TZR_types.h
+++ b/headers/TZR_types.h
@@ -59,6 +59,7 @@ struct TZR_Config {
 	int target_fps;
 	float ratio;
 	bool pixel_perfect;
+	bool interlace;
 	bool hd_render;
 	bool scale_linear;
 	bool show_cursor;
diff --git a/sources/TZR_DrawBegin.c b/sources/TZR_DrawBegin.c
index 59ac06a..9776f9f 100644
--- a/sources/TZR_DrawBegin.c
+++ b/sources/TZR_DrawBegin.c
@@ -10,6 +10,11 @@ TZR_DrawBegin(void)
 		return sdl_error(-1);
 	if (___tzr_config.hd_render)
 		return 0;
+	if (___tzr_config.interlace) {
+		SDL_Texture *const tmp = ___tzr_target;
+		___tzr_target = ___tzr_target_pre;
+		___tzr_target_pre = tmp;
+	}
 	if (SDL_SetRenderTarget(___tzr_renderer, ___tzr_target) < 0)
 		return sdl_error(-1);
 	return 0;
diff --git a/sources/TZR_DrawEnd.c b/sources/TZR_DrawEnd.c
index a1d09da..070accd 100644
--- a/sources/TZR_DrawEnd.c
+++ b/sources/TZR_DrawEnd.c
@@ -8,6 +8,24 @@
 static int
 pixel_draw_end(void)
 {
+	if (___tzr_config.interlace) {
+		static int odd = 0;
+		odd ^= 1;
+		for (int i = odd; i < ___tzr_config.height; i += 2) {
+			const SDL_Rect rect = {
+				0,
+				i,
+				___tzr_config.width,
+				1
+			};
+			if (SDL_RenderCopy(___tzr_renderer,
+			                   ___tzr_target_pre,
+			                   &rect,
+			                   &rect) < 0)
+				return sdl_error(-1);
+		}
+	}
+
 	if (SDL_SetRenderTarget(___tzr_renderer, NULL) < 0)
 		return sdl_error(-1);
 	if (SDL_SetRenderDrawColor(___tzr_renderer, 0, 0, 0, 255) < 0)
diff --git a/sources/TZR_Init.c b/sources/TZR_Init.c
index 1fd23ee..5af39f4 100644
--- a/sources/TZR_Init.c
+++ b/sources/TZR_Init.c
@@ -75,6 +75,14 @@ _TZR_Init(const TZR_Config *config)
 		                                  ___tzr_config.height);
 		if (___tzr_target == NULL)
 			return _sdl_error();
+		if (___tzr_config.interlace) {
+			___tzr_target_pre = SDL_CreateTexture(
+			    ___tzr_renderer,
+			    SDL_PIXELFORMAT_RGB888,
+			    SDL_TEXTUREACCESS_TARGET,
+			    ___tzr_config.width,
+			    ___tzr_config.height);
+		}
 	}
 
 	SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY,
diff --git a/sources/TZR_Quit.c b/sources/TZR_Quit.c
index 7d819a3..62be0b0 100644
--- a/sources/TZR_Quit.c
+++ b/sources/TZR_Quit.c
@@ -23,6 +23,10 @@ TZR_Quit(void)
 	___tzr_joysticks = NULL;
 	___tzr_joysticks_size = 0;
 	___tzr_joysticks_capacity = 0;
+	if (___tzr_target_pre != NULL) {
+		SDL_DestroyTexture(___tzr_target_pre);
+		___tzr_target = NULL;
+	}
 	if (___tzr_target != NULL) {
 		SDL_DestroyTexture(___tzr_target);
 		___tzr_target = NULL;
diff --git a/sources/globals.c b/sources/globals.c
index a67ebc0..3286499 100644
--- a/sources/globals.c
+++ b/sources/globals.c
@@ -12,6 +12,7 @@ size_t ___tzr_resources_size = 0;
 SDL_Window *___tzr_window = NULL;
 SDL_Renderer *___tzr_renderer = NULL;
 SDL_Texture *___tzr_target = NULL;
+SDL_Texture *___tzr_target_pre = NULL;
 unsigned long ___tzr_tick = 0;
 unsigned long ___tzr_next_time = 0;
 unsigned long ___tzr_min_dt = 0;
-- 
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