Snap output window to framebuffer pixel grid

Author: drhelius

platforms/shared/desktop/gui.cpp

@@ -607,7 +607,7 @@ static void main_window(void)
     }
 
     float tex_h = (float)runtime.screen_width / (float)(SYSTEM_TEXTURE_WIDTH);
-    float tex_v = (float)runtime.screen_height / (float)(SYSTEM_TEXTURE_HEIGHT);
+    float tex_v = ((float)runtime.screen_height * (float)ogl_renderer_output_scale) / (float)(FRAME_BUFFER_HEIGHT);
 
     ImGui::Image((ImTextureID)(intptr_t)ogl_renderer_emu_texture, ImVec2(window_width, window_height), ImVec2(0, 0), ImVec2(tex_h, tex_v));
 

platforms/shared/desktop/ogl_renderer.cpp

@@ -25,10 +25,13 @@
     #include <glad.h>
 #endif
 
+#include <math.h>
+
 #include "imgui.h"
 #include "imgui_impl_opengl3.h"
 #include "emu.h"
 #include "config.h"
+#include "gui.h"
 #include "geargrafx.h"
 
 #define OGL_RENDERER_IMPORT
@@ -48,6 +51,7 @@ static int quad_uniform_color = -1;
 static int quad_uniform_tex_scale = -1;
 static int quad_uniform_viewport_size = -1;
 static int quad_uniform_use_fragcoord = -1;
+static int quad_uniform_scanline_scale = -1;
 
 
 
@@ -65,6 +69,40 @@ static void update_system_texture(void);
 static void update_debug_textures(void);
 static void update_savestates_texture(void);
 static void render_scanlines(void);
+static int compute_output_scale(void);
+
+static int compute_output_scale(void)
+{
+    int scale = FRAME_BUFFER_SCALE_DEFAULT;
+
+    if (!config_video.scanlines || config_debug.debug)
+        return scale;
+
+    ImGuiIO& io = ImGui::GetIO();
+    float fb_scale_x = io.DisplayFramebufferScale.x > 0.0f ? io.DisplayFramebufferScale.x : 1.0f;
+    float fb_scale_y = io.DisplayFramebufferScale.y > 0.0f ? io.DisplayFramebufferScale.y : 1.0f;
+    bool fractional_fb_scale = (fabsf(fb_scale_x - roundf(fb_scale_x)) > 0.001f) || (fabsf(fb_scale_y - roundf(fb_scale_y)) > 0.001f);
+
+    if (!fractional_fb_scale)
+        return scale;
+
+    if (config_video.scale == 1)
+    {
+        scale = config_video.scale_manual;
+    }
+    else if ((config_video.scale == 0) && (current_runtime.screen_height > 0) && (gui_main_window_height > 0))
+    {
+        int physical_height = (int)roundf((float)gui_main_window_height * fb_scale_y);
+        scale = physical_height / current_runtime.screen_height;
+    }
+
+    if (scale < 1)
+        scale = 1;
+    if (scale > FRAME_BUFFER_SCALE)
+        scale = FRAME_BUFFER_SCALE;
+
+    return scale;
+}
 
 bool ogl_renderer_init(void)
 {
@@ -134,6 +172,7 @@ void ogl_renderer_begin_render(void)
 void ogl_renderer_render(void)
 {
     emu_get_runtime(current_runtime);
+    ogl_renderer_output_scale = compute_output_scale();
 
     if (config_debug.debug)
     {
@@ -302,7 +341,7 @@ static void render_emu_mix(void)
     update_system_texture();
 
     int viewportWidth = current_runtime.screen_width;
-    int viewportHeight = current_runtime.screen_height * FRAME_BUFFER_SCALE;
+    int viewportHeight = current_runtime.screen_height * ogl_renderer_output_scale;
 
     glUseProgram(quad_shader_program);
     glUniform2f(quad_uniform_tex_scale, tex_h, tex_v);
@@ -403,7 +442,7 @@ static void update_emu_texture(void)
 static void render_quad(float tex_h, float tex_v)
 {
     int viewportWidth = current_runtime.screen_width;
-    int viewportHeight = current_runtime.screen_height * FRAME_BUFFER_SCALE;
+    int viewportHeight = current_runtime.screen_height * ogl_renderer_output_scale;
 
     glUseProgram(quad_shader_program);
     glUniform2f(quad_uniform_tex_scale, tex_h, tex_v);
@@ -426,7 +465,7 @@ static void render_scanlines(void)
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
     int viewportWidth = current_runtime.screen_width;
-    int viewportHeight = current_runtime.screen_height * FRAME_BUFFER_SCALE;
+    int viewportHeight = current_runtime.screen_height * ogl_renderer_output_scale;
 
     float tex_h = (float)current_runtime.screen_width;
     float tex_v = (float)current_runtime.screen_height;
@@ -435,6 +474,7 @@ static void render_scanlines(void)
     glUniform2f(quad_uniform_tex_scale, tex_h, tex_v);
     glUniform2f(quad_uniform_viewport_size, (float)viewportWidth, (float)viewportHeight);
     glUniform1i(quad_uniform_use_fragcoord, 2);
+    glUniform1i(quad_uniform_scanline_scale, ogl_renderer_output_scale);
     glUniform4f(quad_uniform_color, 1.0f, 1.0f, 1.0f, config_video.scanlines_intensity);
 
     glViewport(0, 0, viewportWidth, viewportHeight);
@@ -475,10 +515,11 @@ static void init_shaders(void)
         "uniform vec2 uTexScale;\n"
         "uniform vec2 uViewportSize;\n"
         "uniform int uUseFragCoord;\n"
+        "uniform int uScanlineScale;\n"
         "void main() {\n"
         "    if (uUseFragCoord == 2) {\n"
-        "        float row = mod(floor(gl_FragCoord.y), 4.0);\n"
-        "        float mask = row >= 2.0 ? 1.0 : 0.0;\n"
+        "        float row = mod(floor(gl_FragCoord.y), float(uScanlineScale));\n"
+        "        float mask = row >= (float(uScanlineScale) * 0.5) ? 1.0 : 0.0;\n"
         "        FragColor = vec4(0.0, 0.0, 0.0, uColor.a * mask);\n"
         "        return;\n"
         "    }\n"
@@ -538,10 +579,12 @@ static void init_shaders(void)
     quad_uniform_color = glGetUniformLocation(quad_shader_program, "uColor");
     quad_uniform_viewport_size = glGetUniformLocation(quad_shader_program, "uViewportSize");
     quad_uniform_use_fragcoord = glGetUniformLocation(quad_shader_program, "uUseFragCoord");
+    quad_uniform_scanline_scale = glGetUniformLocation(quad_shader_program, "uScanlineScale");
 
     glUseProgram(quad_shader_program);
     glUniform1i(quad_uniform_texture, 0);
     glUniform1i(quad_uniform_use_fragcoord, 0);
+    glUniform1i(quad_uniform_scanline_scale, FRAME_BUFFER_SCALE_DEFAULT);
     glUseProgram(0);
 
     float quad_vertices[] = {

platforms/shared/desktop/ogl_renderer.h

@@ -28,7 +28,8 @@
     #define EXTERN extern
 #endif
 
-#define FRAME_BUFFER_SCALE 4
+#define FRAME_BUFFER_SCALE 10
+#define FRAME_BUFFER_SCALE_DEFAULT 4
 #define SYSTEM_TEXTURE_WIDTH 2048
 #define SYSTEM_TEXTURE_HEIGHT 512
 #define FRAME_BUFFER_WIDTH (SYSTEM_TEXTURE_WIDTH * 1)
@@ -40,6 +41,7 @@ EXTERN uint32_t ogl_renderer_emu_debug_huc6270_sprites[2][64];
 EXTERN uint32_t ogl_renderer_emu_debug_huc6270_tiles[2];
 EXTERN uint32_t ogl_renderer_emu_savestates;
 EXTERN const char* ogl_renderer_opengl_version;
+EXTERN int ogl_renderer_output_scale;
 
 EXTERN bool ogl_renderer_init(void);
 EXTERN void ogl_renderer_destroy(void);