From 5291b193e2f4ac882d6b1acca3438c2f7cc08637 Mon Sep 17 00:00:00 2001
From: Michael Fabian 'Xaymar' Dirks <info@xaymar.com>
Date: Thu, 23 Apr 2020 07:56:12 +0200
Subject: [PATCH] gfx-shader: Fix rendering at unexpected sizes and fix
 performance

Fixes rendering at unexpected sizes by first rendering to a render target and then rendering the contents of that render target to the frame buffer instead. This also prevent rendering twice or more, which might cause severe FPS impact.
---
 source/gfx/shader/gfx-shader.cpp | 23 +++++++++++++++++++++--
 source/gfx/shader/gfx-shader.hpp |  5 +++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/source/gfx/shader/gfx-shader.cpp b/source/gfx/shader/gfx-shader.cpp
index 353b8bc..d651b27 100644
--- a/source/gfx/shader/gfx-shader.cpp
+++ b/source/gfx/shader/gfx-shader.cpp
@@ -39,7 +39,9 @@ gfx::shader::shader::shader(obs_source_t* self, shader_mode mode)
 
 	  _width_type(size_type::Percent), _width_value(1.0), _height_type(size_type::Percent), _height_value(1.0),
 
-	  _time(0), _time_loop(0), _loops(0), _random(), _have_current_params(false)
+	  _time(0), _time_loop(0), _loops(0), _random(), _have_current_params(false),
+
+	  _rt_up_to_date(false), _rt(std::make_shared<gs::rendertarget>(GS_RGBA, GS_ZS_NONE))
 {
 	_random.seed(static_cast<unsigned long long>(time(NULL)));
 }
@@ -453,6 +455,8 @@ void gfx::shader::shader::prepare_render()
 						  1.0f / static_cast<float_t>(width()), 1.0f / static_cast<float_t>(height()));
 		}
 	}
+
+	_rt_up_to_date = false;
 }
 
 void gfx::shader::shader::render()
@@ -460,7 +464,22 @@ void gfx::shader::shader::render()
 	if (!_shader)
 		return;
 
-	while (gs_effect_loop(_shader.get_object(), _shader_tech.c_str())) {
+	if (!_rt_up_to_date) {
+		auto op   = _rt->render(width(), height());
+		vec4 zero = {0, 0, 0, 0};
+		gs_ortho(0, width(), 0, height(), 0, 1);
+		gs_clear(GS_CLEAR_COLOR, &zero, 0, 0);
+		gs_enable_blending(true);
+		gs_blend_function(GS_BLEND_ONE, GS_BLEND_ZERO);
+		gs_enable_color(true, true, true, true);
+		while (gs_effect_loop(_shader.get_object(), _shader_tech.c_str())) {
+			gs_draw_sprite(nullptr, 0, width(), height());
+		}
+	}
+
+	gs_effect_set_texture(gs_effect_get_param_by_name(obs_get_base_effect(OBS_EFFECT_DEFAULT), "image"),
+						  _rt->get_texture()->get_object());
+	while (gs_effect_loop(obs_get_base_effect(OBS_EFFECT_DEFAULT), "Draw")) {
 		gs_draw_sprite(nullptr, 0, width(), height());
 	}
 }
diff --git a/source/gfx/shader/gfx-shader.hpp b/source/gfx/shader/gfx-shader.hpp
index b585c93..3497cf3 100644
--- a/source/gfx/shader/gfx-shader.hpp
+++ b/source/gfx/shader/gfx-shader.hpp
@@ -23,6 +23,7 @@
 #include <random>
 #include "gfx/shader/gfx-shader-param.hpp"
 #include "obs/gs/gs-effect.hpp"
+#include "obs/gs/gs-rendertarget.hpp"
 
 namespace gfx {
 	namespace shader {
@@ -69,6 +70,10 @@ namespace gfx {
 			std::mt19937_64 _random;
 			bool            _have_current_params;
 
+			// Rendering
+			bool                              _rt_up_to_date;
+			std::shared_ptr<gs::rendertarget> _rt;
+
 			public:
 			shader(obs_source_t* self, shader_mode mode);
 			~shader();