From 886a92f3e035dabb5652ab2f1f1fb73ead47416f Mon Sep 17 00:00:00 2001
From: Wojciech Graj <wojtek.graj.2004@gmail.com>
Date: Mon, 2 May 2022 17:13:40 +0200
Subject: [PATCH] Fix strobing.

---
 demodir/termgl_demo.c |  8 +++++---
 lib/termgl.h          |  9 ++++++++-
 src/termgl.c          | 13 +++++++++++--
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/demodir/termgl_demo.c b/demodir/termgl_demo.c
index a636fc0..55da5ed 100644
--- a/demodir/termgl_demo.c
+++ b/demodir/termgl_demo.c
@@ -129,7 +129,7 @@ void demo_mandelbrot(const unsigned res_x, const unsigned res_y, const unsigned
 {
 	TGL *tgl = tgl_init(res_x, res_y, &gradient_full);
 	assert(tgl);
-	assert(!tgl_enable(tgl, TGL_OUTPUT_BUFFER));
+	assert(!tgl_enable(tgl, TGL_OUTPUT_BUFFER | TGL_PROGRESSIVE));
 
 	const unsigned frame_max = 90;
 	const unsigned i_max = 255;
@@ -199,7 +199,7 @@ void demo_teapot(const unsigned res_x, const unsigned res_y, const unsigned fram
 	assert(tgl);
 	assert(!tgl3d_init(tgl));
 	tgl3d_cull_face(tgl, TGL_BACK | TGL_CCW);
-	assert(!tgl_enable(tgl, TGL_DOUBLE_CHARS | TGL_CULL_FACE | TGL_Z_BUFFER | TGL_OUTPUT_BUFFER));
+	assert(!tgl_enable(tgl, TGL_DOUBLE_CHARS | TGL_CULL_FACE | TGL_Z_BUFFER | TGL_OUTPUT_BUFFER | TGL_PROGRESSIVE));
 	tgl3d_camera(tgl, 1.57f, 0.1f, 5.f);
 
 	// Load triangles
@@ -291,7 +291,7 @@ void demo_star(const unsigned res_x, const unsigned res_y, const unsigned framet
 {
 	TGL *tgl = tgl_init(res_x, res_y, &gradient_min);
 	assert(tgl);
-	assert(!tgl_enable(tgl, TGL_OUTPUT_BUFFER));
+	assert(!tgl_enable(tgl, TGL_OUTPUT_BUFFER | TGL_PROGRESSIVE));
 
 	const float pi2 = 6.28319f;
 	const unsigned n = 8, d = 3;
@@ -381,6 +381,7 @@ int main(int argc, char **argv)
 	(void)argc;
 	(void)argv;
 
+	tgl_clear_screen();
 	puts(HELPTEXT_HEADER);
 	unsigned col, row;
 	tglutil_get_console_size(&col, &row, true);
@@ -389,6 +390,7 @@ int main(int argc, char **argv)
 
 	unsigned n = 0;
 	assert(scanf("%u", &n) == 1);
+	tgl_clear_screen();
 
 	switch (n) {
 	case 1u:
diff --git a/lib/termgl.h b/lib/termgl.h
index 5657437..70527dd 100644
--- a/lib/termgl.h
+++ b/lib/termgl.h
@@ -49,8 +49,9 @@ enum {
 	TGL_Z_BUFFER = 0x04,
 /* settings */
 	TGL_DOUBLE_CHARS = 0x10,
+	TGL_PROGRESSIVE = 0x20,
 #ifdef TERMGL3D
-	TGL_CULL_FACE = 0x20,
+	TGL_CULL_FACE = 0x40,
 #endif
 };
 
@@ -93,6 +94,11 @@ int tgl_flush(TGL *tgl);
  */
 void tgl_clear(TGL *tgl, uint8_t buffers);
 
+/**
+ * Clears the screen
+ */
+void tgl_clear_screen(void);
+
 /**
  * Enables or disables certain settings
  * @param settings: bitwise combination of settings:
@@ -100,6 +106,7 @@ void tgl_clear(TGL *tgl, uint8_t buffers);
  *   TGL_DOUBLE_CHARS - square pixels by printing 2 characters per pixel
  *   TGL_CULL_FACE - (3D ONLY) cull specified triangle faces
  *   TGL_OUTPUT_BUFFER - output buffer allowing for just one print to flush. Mush faster on most terminals, but requires a few hundred kilobytes of memory
+ *   TGL_PROGRESSIVE - Over-write previous frame. Eliminates strobing but requires call to tgl_clear_screen before drawing smaller image and after resizing terminal if terminal size was smaller than frame size
  * @return 0 on success, -1 on failure
  * On failure, errno is set to value specified by: https://www.man7.org/linux/man-pages/man3/malloc.3.html#ERRORS
  */
diff --git a/src/termgl.c b/src/termgl.c
index c9acbc2..8ad13bd 100644
--- a/src/termgl.c
+++ b/src/termgl.c
@@ -9,7 +9,7 @@
 /**
  * Setting MACROs
  */
-#define TGL_CLEAR_SCREEN do {fputs("\033[1;1H\033[2J", stdout);} while (0)
+#define TGL_CLEAR_SCR do {fputs("\033[1;1H\033[2J", stdout);} while (0)
 #define TGL_TYPEOF __typeof__
 #define TGL_MALLOC malloc
 #define TGL_FREE free
@@ -122,6 +122,11 @@ void tgl_clear(TGL * const tgl, const uint8_t buffers)
 		memset(tgl->output_buffer, '\0', tgl->output_buffer_size);
 }
 
+void tgl_clear_screen(void)
+{
+	TGL_CLEAR_SCR;
+}
+
 TGL *tgl_init(const unsigned width, const unsigned height, const TGLGradient * gradient)
 {
 #ifdef TGL_OS_WINDOWS
@@ -224,7 +229,11 @@ char *itgl_generate_sgr(const uint16_t color_prev, const uint16_t color_cur, cha
 
 int tgl_flush(TGL * const tgl)
 {
-	TGL_CLEAR_SCREEN;
+	if (tgl->settings & TGL_PROGRESSIVE)
+		CALL_STDOUT(fputs("\033[;H", stdout), -1);
+	else
+		TGL_CLEAR_SCR;
+
 	uint16_t color = 0x0007;
 	unsigned row, col;
 	Pixel *pixel = tgl->frame_buffer;