commit 8edbbe8acfc2ac01a9e2d202692cf37eeee5c325
Author:     Jonathan Dowland <jon+github@alcopop.org>
AuthorDate: Mon Feb 20 18:16:13 2017 +0000
Commit:     Jonathan Dowland <jon+github@alcopop.org>
CommitDate: Mon Feb 20 18:16:13 2017 +0000

    VGA porch emulation: make optional

    Based on feedback.
---
 src/i_video.c       | 17 +++++++++++++----
 src/i_video.h       |  1 +
 src/m_config.c      |  7 +++++++
 src/setup/display.c |  4 ++++
 4 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/i_video.c b/src/i_video.c
index 759d9776..73707f9a 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -126,6 +126,10 @@ int fullscreen = true;

 int aspect_ratio_correct = true;

+// VGA Porch palette change emulation
+
+int vga_porch_flash = false;
+
 // Force software rendering, for systems which lack effective hardware
 // acceleration

@@ -740,11 +744,15 @@ void I_FinishUpdate (void)
     if (palette_to_set)
     {
         SDL_SetPaletteColors(screenbuffer->format->palette, palette, 0, 256);
-        // "flash" the pillars/letterboxes with palette changes, emulating
-        // VGA "porch" behaviour (GitHub issue #832)
-        SDL_SetRenderDrawColor(renderer, palette[0].r, palette[0].g,
-            palette[0].b, SDL_ALPHA_OPAQUE);
         palette_to_set = false;
+
+        if (vga_porch_flash)
+        {
+            // "flash" the pillars/letterboxes with palette changes, emulating
+            // VGA "porch" behaviour (GitHub issue #832)
+            SDL_SetRenderDrawColor(renderer, palette[0].r, palette[0].g,
+                palette[0].b, SDL_ALPHA_OPAQUE);
+        }
     }

     // Blit from the paletted 8-bit screen buffer to the intermediate
@@ -1393,6 +1401,7 @@ void I_BindVideoVariables(void)
     M_BindIntVariable("fullscreen",                &fullscreen);
     M_BindIntVariable("video_display",             &video_display);
     M_BindIntVariable("aspect_ratio_correct",      &aspect_ratio_correct);
+    M_BindIntVariable("vga_porch_flash",           &vga_porch_flash);
     M_BindIntVariable("startup_delay",             &startup_delay);
     M_BindIntVariable("fullscreen_width",          &fullscreen_width);
     M_BindIntVariable("fullscreen_height",         &fullscreen_height);
diff --git a/src/i_video.h b/src/i_video.h
index a4ac1a79..3184bae3 100644
--- a/src/i_video.h
+++ b/src/i_video.h
@@ -90,6 +90,7 @@ extern int screen_width;
 extern int screen_height;
 extern int fullscreen;
 extern int aspect_ratio_correct;
+extern int vga_porch_flash;
 extern int force_software_renderer;

 #endif
diff --git a/src/m_config.c b/src/m_config.c
index bf215e27..9bc96782 100644
--- a/src/m_config.c
+++ b/src/m_config.c
@@ -727,6 +727,13 @@ static default_t extra_defaults_list[] =

     CONFIG_VARIABLE_INT(aspect_ratio_correct),

+    //!
+    // If non-zero, any pillar/letter boxes drawn around the game area
+    // will "flash" when the game palette changes, simulating the VGA
+    // "porch"
+
+    CONFIG_VARIABLE_INT(vga_porch_flash),
+
     //!
     // Window width when running in windowed mode.
     //
diff --git a/src/setup/display.c b/src/setup/display.c
index 9db3cc57..e9533c89 100644
--- a/src/setup/display.c
+++ b/src/setup/display.c
@@ -66,6 +66,7 @@ static window_size_t window_sizes_scaled[] =
 static char *video_driver = "";
 static char *window_position = "";
 static int aspect_ratio_correct = 1;
+static int vga_porch_flash = 0;
 static int force_software_renderer = 0;
 static int fullscreen = 1;
 static int fullscreen_width = 0, fullscreen_height = 0;
@@ -205,6 +206,8 @@ static void AdvancedDisplayConfig(TXT_UNCAST_ARG(widget),
         TXT_NewCheckBox("Save screenshots in PNG format",
                         &png_screenshots),
 #endif
+        TXT_NewCheckBox("Flash borders (VGA porch emulation)",
+                        &vga_porch_flash),
         NULL);

     TXT_SignalConnect(ar_checkbox, "changed", GenerateSizesTable, sizes_table);
@@ -260,6 +263,7 @@ void BindDisplayVariables(void)
     M_BindStringVariable("window_position",        &window_position);
     M_BindIntVariable("usegamma",                  &usegamma);
     M_BindIntVariable("png_screenshots",           &png_screenshots);
+    M_BindIntVariable("vga_porch_flash",           &vga_porch_flash);
     M_BindIntVariable("force_software_renderer",   &force_software_renderer);
     M_BindIntVariable("max_scaling_buffer_pixels", &max_scaling_buffer_pixels);