Update integer scaling.

This fixes a scaling issue where xemu scales the framebuffer against the size of the window.
Uneven scaling would cause the texture to become blurry, or misaligned.
Instead, we just render the framebuffer at a single size and adjust the position using offsets.

Author: jyetcv

ui/xui/gl-helpers.cc

@@ -884,14 +884,14 @@ void ScaleDimensions(int src_width, int src_height, int max_width, int max_heigh
     }
 }
 
-void RenderFramebuffer(GLint tex, int width, int height, bool flip, float scale[2])
+void RenderFramebuffer(GLint tex, int offset_x, int offset_y, int width, int height, bool flip, float scale[2])
 {
     glActiveTexture(GL_TEXTURE0);
     glBindTexture(GL_TEXTURE_2D, tex);
 
     DecalShader *s = g_framebuffer_shader;
     s->flip = flip;
-    glViewport(0, 0, width, height);
+    glViewport(offset_x, offset_y, width, height);
     glUseProgram(s->prog);
     glBindVertexArray(s->vao);
     glUniform1i(s->flipy_loc, s->flip);
@@ -933,6 +933,7 @@ void RenderFramebuffer(GLint tex, int width, int height, bool flip)
 {
     int tw, th;
     float scale[2];
+    int offset_x = 0, offset_y = 0;
 
     glActiveTexture(GL_TEXTURE0);
     glBindTexture(GL_TEXTURE_2D, tex);
@@ -952,12 +953,18 @@ void RenderFramebuffer(GLint tex, int width, int height, bool flip)
     } else if (g_config.display.ui.fit == CONFIG_DISPLAY_UI_FIT_INTEGER) {
         // Integer scaling
         float t_ratio = GetDisplayAspectRatio(tw, th);
-        int s_factor = (float)width/(float)tw;
-        int s_height = (float)height/(float)th;
-        if (s_height < s_factor) s_factor = s_height;
-        if (s_factor < 1) s_factor = 1;
-            scale[0] = s_factor*t_ratio*(int)th/(float)width;
-            scale[1] = s_factor*(int)th/(float)height;
+        int factor = width / (th * t_ratio);
+        int factor_h = height / th;
+        factor = (factor_h < factor) ? factor_h : factor;
+        factor = (factor <= 1) ? 1 : factor;
+        int fb_height = th * factor;
+        int fb_width = (int)(fb_height * t_ratio);
+        offset_x = (width - fb_width) / 2;
+        offset_y = (height - fb_height) / 2;
+        width = fb_width;
+        height = fb_height;
+        scale[0] = 1.0;
+        scale[1] = 1.0;
     } else {
         float t_ratio = GetDisplayAspectRatio(tw, th);
         float w_ratio = (float)width/(float)height;
@@ -970,12 +977,13 @@ void RenderFramebuffer(GLint tex, int width, int height, bool flip)
         }
     }
 
-    RenderFramebuffer(tex, width, height, flip, scale);
+    RenderFramebuffer(tex, offset_x, offset_y, width, height, flip, scale);
 }
 
 bool RenderFramebufferToPng(GLuint tex, bool flip, std::vector<uint8_t> &png, int max_width, int max_height)
 {
     int width, height;
+    int offset_x = 0, offset_y = 0;
 
     glActiveTexture(GL_TEXTURE0);
     glBindTexture(GL_TEXTURE_2D, tex);
@@ -996,7 +1004,7 @@ bool RenderFramebufferToPng(GLuint tex, bool flip, std::vector<uint8_t> &png, in
     bool blend = glIsEnabled(GL_BLEND);
     if (blend) glDisable(GL_BLEND);
     float scale[2] = {1.0, 1.0};
-    RenderFramebuffer(tex, width, height, !flip, scale);
+    RenderFramebuffer(tex, offset_x, offset_y, width, height, !flip, scale);
     if (blend) glEnable(GL_BLEND);
     glPixelStorei(GL_PACK_ROW_LENGTH, width);
     glPixelStorei(GL_PACK_IMAGE_HEIGHT, height);

ui/xui/gl-helpers.hh

@@ -50,7 +50,7 @@ void RenderControllerPort(float frame_x, float frame_y, int i,
 void RenderXmu(float frame_x, float frame_y, uint32_t primary_color,
                uint32_t secondary_color);
 void RenderFramebuffer(GLint tex, int width, int height, bool flip);
-void RenderFramebuffer(GLint tex, int width, int height, bool flip, float scale[2]);
+void RenderFramebuffer(GLint tex, int offset_x, int offset_y, int width, int height, bool flip, float scale[2]);
 bool RenderFramebufferToPng(GLuint tex, bool flip, std::vector<uint8_t> &png, int max_width = 0, int max_height = 0);
 void SaveScreenshot(GLuint tex, bool flip);
 void ScaleDimensions(int src_width, int src_height, int max_width, int max_height, int *out_width, int *out_height);