From fea6833ea00efefec5dccd2ee85656e759726168 Mon Sep 17 00:00:00 2001
From: Roman Fomin <rfomin@gmail.com>
Date: Wed, 20 Dec 2023 14:09:01 +0700
Subject: [PATCH 1/5] update DRS parameters

---
 src/d_main.c   | 16 ++++++----------
 src/doomstat.h |  2 --
 src/i_video.c  | 40 ++++++++++++++++++++++------------------
 src/i_video.h  | 10 ++++++----
 4 files changed, 34 insertions(+), 34 deletions(-)

diff --git a/src/d_main.c b/src/d_main.c
index ad289eeb..0d5fdf59 100644
--- a/src/d_main.c
+++ b/src/d_main.c
@@ -210,7 +210,6 @@ void D_ProcessEvents (void)
 gamestate_t    wipegamestate = GS_DEMOSCREEN;
 boolean        screen_melt = true;
 extern int     showMessages;
-boolean        enable_drs;
 
 void D_Display (void)
 {
@@ -246,10 +245,14 @@ void D_Display (void)
     }
   }
 
-  enable_drs = true;
-
   redrawsbar = false;
 
+  // save the current screen if about to wipe
+  if ((wipe = gamestate != wipegamestate) && NOTSTRICTMODE(screen_melt))
+    wipe_StartScreen(0, 0, video.unscaledw, SCREENHEIGHT);
+  else
+    I_DynamicResolution();
+
   if (setsizeneeded)                // change the view size if needed
     {
       R_ExecuteSetViewSize();
@@ -257,13 +260,6 @@ void D_Display (void)
       borderdrawcount = 3;
     }
 
-  // save the current screen if about to wipe
-  if ((wipe = gamestate != wipegamestate) && NOTSTRICTMODE(screen_melt))
-    {
-      enable_drs = false;
-      wipe_StartScreen(0, 0, video.unscaledw, SCREENHEIGHT);
-    }
-
   if (gamestate == GS_LEVEL && gametic)
     HU_Erase();
 
diff --git a/src/doomstat.h b/src/doomstat.h
index 6f30d5f7..8bccef38 100644
--- a/src/doomstat.h
+++ b/src/doomstat.h
@@ -368,8 +368,6 @@ extern  boolean precache;
 //  to force a wipe on the next draw
 extern  gamestate_t     wipegamestate;
 
-extern  boolean         enable_drs;
-
 extern  int             mouseSensitivity_horiz; // killough
 extern  int             mouseSensitivity_vert;
 extern  int             mouseSensitivity_horiz_strafe; // [FG] strafe
diff --git a/src/i_video.c b/src/i_video.c
index 3f3c903d..9377ccea 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -479,7 +479,7 @@ static int targetrefresh;
 static void ResetResolution(int height);
 static void ResetLogicalSize(void);
 
-static void DynamicResolution(void)
+void I_DynamicResolution(void)
 {
     if (resolution_mode != RES_DRS || frametime_withoutpresent == 0 ||
         frametime_withoutpresent > 1000000 / 15)
@@ -494,9 +494,10 @@ static void DynamicResolution(void)
     double actualpercent = actual / target;
 
     #define DRS_MIN_HEIGHT 400
-    #define DRS_DELTA 0.5
+    #define DRS_DELTA 0.01
     #define DRS_GREATER (1 + DRS_DELTA)
     #define DRS_LESS (1 - DRS_DELTA)
+    #define DRS_STEP (SCREENHEIGHT / 2)
 
     int newheight = 0;
     int oldheight = video.height;
@@ -516,6 +517,15 @@ static void DynamicResolution(void)
         return;
     }
 
+    int mul = (newheight + (DRS_STEP - 1)) / DRS_STEP; // integer round
+
+    newheight = mul * DRS_STEP;
+
+    if (newheight > native_height_adjusted)
+    {
+        newheight -= DRS_STEP;
+    }
+
     if (newheight == oldheight)
     {
         return;
@@ -563,8 +573,8 @@ void I_FinishUpdate(void)
 
         time = frametime_start - last_time;
 
-        // Update FPS counter every second
-        if (time >= 1000000)
+        // Update FPS counter every 10th of second
+        if (time >= 100000)
         {
             fps = (frame_counter * 1000000) / time;
             frame_counter = 0;
@@ -590,11 +600,6 @@ void I_FinishUpdate(void)
         I_ResetScreen();
         need_reset = false;
     }
-    else if (enable_drs)
-    {
-        DynamicResolution();
-        enable_drs = false;
-    }
 
     if (need_resize)
     {
@@ -966,14 +971,16 @@ static void ResetResolution(int height)
 {
     int w, h;
 
+    int unscaled_ah = use_aspect ? ACTUALHEIGHT : SCREENHEIGHT;
+
     actualheight = use_aspect ? (int)(height * 1.2) : height;
     video.height = height;
 
     switch (widescreen)
     {
         case RATIO_ORIG:
-            w = 4;
-            h = 3;
+            w = SCREENWIDTH;
+            h = unscaled_ah;
             break;
         case RATIO_MATCH_SCREEN:
             w = native_width;
@@ -1004,14 +1011,11 @@ static void ResetResolution(int height)
         aspect_ratio = 2.4;
     }
 
-    video.unscaledw = (int)(ACTUALHEIGHT * aspect_ratio);
-    video.width = (int)(actualheight * aspect_ratio);
+    video.unscaledw = (int)(unscaled_ah * aspect_ratio);
 
-    // width and height shoud be even
-    video.unscaledw = (video.unscaledw  + 1) & ~1;
-    video.width     = (video.width + 1) & ~1;
-    video.height    = (video.height + 1) & ~1;
-    actualheight    = (actualheight + 1) & ~1;
+    double vertscale = (double)actualheight / (double)unscaled_ah;
+    video.width = (int)(video.unscaledw * vertscale);
+    video.width = (video.width + 1) & ~1;
 
     video.deltaw = (video.unscaledw - NONWIDEWIDTH) / 2;
 
diff --git a/src/i_video.h b/src/i_video.h
index 2b6b01d4..8a564916 100644
--- a/src/i_video.h
+++ b/src/i_video.h
@@ -51,20 +51,22 @@ typedef enum
 // determines the hardware configuration
 // and sets up the video mode
 
-void I_InitGraphics (void);
+void I_InitGraphics(void);
 void I_ShutdownGraphics(void);
 
 // Takes full 8 bit values.
-void I_SetPalette (byte* palette);
+void I_SetPalette(byte* palette);
 
-void I_FinishUpdate (void);
+void I_FinishUpdate(void);
 
-void I_ReadScreen (byte* scr);
+void I_ReadScreen(byte* dst);
 
 void I_ResetScreen(void);   // killough 10/98
 void I_ResetTargetRefresh(void);
 void I_ToggleVsync(void); // [JN] Calls native SDL vsync toggle
 
+void I_DynamicResolution(void);
+
 extern boolean use_vsync;  // killough 2/8/98: controls whether vsync is called
 extern boolean disk_icon;  // killough 10/98
 extern resolution_mode_t resolution_mode, default_resolution_mode;

From 9f0197338f9b024bfc8d87ab8432796259c58062 Mon Sep 17 00:00:00 2001
From: Roman Fomin <rfomin@gmail.com>
Date: Wed, 20 Dec 2023 14:09:26 +0700
Subject: [PATCH 2/5] introduce video.pitch, avoid screen copying in
 I_FinishUpdate

---
 src/f_wipe.c     |  8 ++++----
 src/i_video.c    | 30 ++++++++----------------------
 src/m_snapshot.c |  7 +++----
 src/r_draw.c     |  4 ++--
 src/r_voxel.c    |  2 +-
 src/st_stuff.c   | 13 +++----------
 src/v_video.c    |  2 +-
 src/v_video.h    |  1 +
 8 files changed, 23 insertions(+), 44 deletions(-)

diff --git a/src/f_wipe.c b/src/f_wipe.c
index 8cdc012a..025d047d 100644
--- a/src/f_wipe.c
+++ b/src/f_wipe.c
@@ -55,7 +55,7 @@ static void wipe_shittyColMajorXform(byte *array, int width, int height)
 
 static int wipe_initColorXForm(int width, int height, int ticks)
 {
-  memcpy(wipe_scr, wipe_scr_start, width*height);
+  V_PutBlock(0, 0, width, height, wipe_scr_start);
   return 0;
 }
 
@@ -94,7 +94,7 @@ static int wipe_initMelt(int width, int height, int ticks)
   col_y = Z_Malloc(num_columns * sizeof(*col_y), PU_STATIC, NULL);
 
   // copy start screen to main screen
-  memcpy(wipe_scr, wipe_scr_start, width*height);
+  V_PutBlock(0, 0, width, height, wipe_scr_start);
 
   // makes this wipe faster (in theory)
   // to have stuff in column-major format
@@ -152,14 +152,14 @@ static int wipe_doMelt(int width, int height, int ticks)
     for (y = 0; y < scroff; ++y)
     {
       *d = *s;
-      d += width;
+      d += video.pitch;
       s++;
     }
     s = wipe_scr_start + x * height;
     for (; y < height; ++y)
     {
       *d = *s;
-      d += width;
+      d += video.pitch;
       s++;
     }
   }
diff --git a/src/i_video.c b/src/i_video.c
index 9377ccea..f37d5621 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -436,20 +436,6 @@ void I_StartFrame(void)
 
 static void UpdateRender(void)
 {
-    int i;
-
-    // Copy linear video buffer to rectangle on surface
-
-    byte *dest = screenbuffer->pixels;
-    const pixel_t *src = I_VideoBuffer;
-
-    for (i = 0; i < blit_rect.h; ++i)
-    {
-        memcpy(dest, src, blit_rect.w);
-        dest += screenbuffer->w;
-        src += blit_rect.w;
-    }
-
     SDL_LowerBlit(screenbuffer, &blit_rect, argbbuffer, &blit_rect);
     SDL_UpdateTexture(texture, &blit_rect, argbbuffer->pixels, argbbuffer->pitch);
     SDL_RenderClear(renderer);
@@ -639,9 +625,9 @@ void I_FinishUpdate(void)
 // I_ReadScreen
 //
 
-void I_ReadScreen(byte *scr)
+void I_ReadScreen(byte *dst)
 {
-   memcpy(scr, I_VideoBuffer, video.width * video.height * sizeof(*I_VideoBuffer));
+    V_GetBlock(0, 0, video.width, video.height, dst);
 }
 
 //
@@ -1381,6 +1367,8 @@ static void CreateSurfaces(void)
     w = (w + 3) & ~3;
     h = (h + 3) & ~3;
 
+    video.pitch = w;
+
     // [FG] create paletted frame buffer
 
     if (screenbuffer != NULL)
@@ -1393,14 +1381,12 @@ static void CreateSurfaces(void)
                                         0, 0, 0, 0);
     SDL_FillRect(screenbuffer, NULL, 0);
 
-    if (I_VideoBuffer != NULL)
-    {
-        Z_Free(I_VideoBuffer);
-    }
-
-    I_VideoBuffer = Z_Calloc(1, w * h * sizeof(*I_VideoBuffer), PU_STATIC, NULL);
+    I_VideoBuffer = screenbuffer->pixels;
     V_RestoreBuffer();
 
+    // Clear the screen to black.
+    memset(I_VideoBuffer, 0, w * h * sizeof(*I_VideoBuffer));
+
     if (argbbuffer != NULL)
     {
         SDL_FreeSurface(argbbuffer);
diff --git a/src/m_snapshot.c b/src/m_snapshot.c
index 3c0985d0..6c001529 100644
--- a/src/m_snapshot.c
+++ b/src/m_snapshot.c
@@ -21,7 +21,6 @@
 #include "doomtype.h"
 #include "doomstat.h"
 
-#include "i_video.h"
 #include "m_io.h"
 #include "v_video.h"
 #include "r_main.h"
@@ -123,7 +122,7 @@ static void M_TakeSnapshot (void)
   {
     for (x = video.deltaw; x < NONWIDEWIDTH + video.deltaw; x++)
     {
-      *p++ = s[V_ScaleY(y) * video.width + V_ScaleX(x)];
+      *p++ = s[V_ScaleY(y) * video.pitch + V_ScaleX(x)];
     }
   }
 
@@ -164,7 +163,7 @@ boolean M_DrawSnapshot (int n, int x, int y, int w, int h)
   const fixed_t step_x = (SCREENWIDTH << FRACBITS) / rect.sw;
   const fixed_t step_y = (SCREENHEIGHT << FRACBITS) / rect.sh;
 
-  byte *dest = I_VideoBuffer + rect.sy * video.width + rect.sx;
+  byte *dest = I_VideoBuffer + rect.sy * video.pitch + rect.sx;
 
   fixed_t srcx, srcy;
   int destx, desty;
@@ -172,7 +171,7 @@ boolean M_DrawSnapshot (int n, int x, int y, int w, int h)
 
   for (desty = 0, srcy = 0; desty < rect.sh; desty++, srcy += step_y)
   {
-    destline = dest + desty * video.width;
+    destline = dest + desty * video.pitch;
     srcline = snapshots[n] + (srcy >> FRACBITS) * SCREENWIDTH;
 
     for (destx = 0, srcx = 0; destx < rect.sw; destx++, srcx += step_x)
diff --git a/src/r_draw.c b/src/r_draw.c
index abbb0f9f..d1df014d 100644
--- a/src/r_draw.c
+++ b/src/r_draw.c
@@ -47,7 +47,7 @@ int  viewwindowx;
 int  viewwindowy; 
 static byte **ylookup = NULL;
 static int  *columnofs = NULL;
-static int  linesize = SCREENWIDTH;  // killough 11/98
+static int  linesize;  // killough 11/98
 
 // Color tables for different players,
 //  translate a limited part to another
@@ -824,7 +824,7 @@ void R_InitBuffer(void)
 {
   int i;
 
-  linesize = video.width;    // killough 11/98
+  linesize = video.pitch;    // killough 11/98
 
   // Handle resize,
   //  e.g. smaller view windows
diff --git a/src/r_voxel.c b/src/r_voxel.c
index 1a3bc2a6..fe42eca6 100644
--- a/src/r_voxel.c
+++ b/src/r_voxel.c
@@ -813,7 +813,7 @@ static void VX_DrawColumn (vissprite_t * spr, int x, int y)
 
 	boolean shadow = ((spr->mobjflags & MF_SHADOW) != 0);
 
-	int linesize = video.width;
+	int linesize = video.pitch;
 	byte * dest = I_VideoBuffer + viewwindowy * linesize + viewwindowx;
 
 	// iterate over screen columns
diff --git a/src/st_stuff.c b/src/st_stuff.c
index 64f4d25a..b837e131 100644
--- a/src/st_stuff.c
+++ b/src/st_stuff.c
@@ -342,7 +342,7 @@ static void ST_DrawSolidBackground(int st_x)
     {
       for (x = 0; x < depth; x++)
       {
-        byte *c = st_backing_screen + V_ScaleY(y) * video.width + V_ScaleX(x + offset);
+        byte *c = st_backing_screen + V_ScaleY(y) * video.pitch + V_ScaleX(x + offset);
         r += pal[3 * c[0] + 0];
         g += pal[3 * c[0] + 1];
         b += pal[3 * c[0] + 2];
@@ -1327,14 +1327,7 @@ void ST_Init(void)
 
 void ST_InitRes(void)
 {
-  vrect_t rect;
-
-  rect.x = 0;
-  rect.y = 0;
-  rect.w = video.unscaledw;
-  rect.h = StatusBarBufferHeight();
-
-  V_ScaleRect(&rect);
+  int height = V_ScaleY(StatusBarBufferHeight());
 
   if (st_backing_screen)
   {
@@ -1342,7 +1335,7 @@ void ST_InitRes(void)
   }
 
   // killough 11/98: allocate enough for hires
-  st_backing_screen = Z_Malloc(rect.sw * rect.sh * sizeof(*st_backing_screen), PU_STATIC, 0);
+  st_backing_screen = Z_Malloc(video.pitch * height * sizeof(*st_backing_screen), PU_STATIC, 0);
 }
 
 void ST_Warnings(void)
diff --git a/src/v_video.c b/src/v_video.c
index d77d2bc4..987ee59f 100644
--- a/src/v_video.c
+++ b/src/v_video.c
@@ -970,7 +970,7 @@ void V_Init(void)
     int i;
     fixed_t frac, lastfrac;
 
-    linesize = video.width;
+    linesize = video.pitch;
 
     video.xscale = (video.width << FRACBITS) / video.unscaledw;
     video.yscale = (video.height << FRACBITS) / SCREENHEIGHT;
diff --git a/src/v_video.h b/src/v_video.h
index 44ec9d25..e4f8cb23 100644
--- a/src/v_video.h
+++ b/src/v_video.h
@@ -93,6 +93,7 @@ typedef struct
 {
     int width;
     int height;
+    int pitch;
     int unscaledw;  // unscaled width with correction for widecreen
     int deltaw;     // widescreen delta
 

From d05570e334bb551f26a9f5f2634642ea963369d4 Mon Sep 17 00:00:00 2001
From: Roman Fomin <rfomin@gmail.com>
Date: Wed, 20 Dec 2023 15:49:31 +0700
Subject: [PATCH 3/5] fix automap and overlay

* Fix background buffer size
---
 src/am_map.c  | 10 ++++++++--
 src/i_video.c |  2 +-
 src/r_draw.c  |  2 +-
 src/v_video.c | 10 +++++++---
 4 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/am_map.c b/src/am_map.c
index 2d81b71c..9a00d1d6 100644
--- a/src/am_map.c
+++ b/src/am_map.c
@@ -1074,7 +1074,13 @@ void AM_Ticker (void)
 //
 static void AM_clearFB(int color)
 {
-  memset(fb, color, f_w*f_h);
+  int h = f_h;
+  byte *src = fb;
+  while (h--)
+  {
+    memset(src, color, f_w);
+    src += video.pitch;
+  }
 }
 
 //
@@ -1252,7 +1258,7 @@ static void AM_drawFline_Vanilla(fline_t* fl, int color)
   }
 #endif
 
-#define PUTDOT(xx,yy,cc) fb[(yy)*f_w+(xx)]=(cc)
+#define PUTDOT(xx,yy,cc) fb[(yy)*video.pitch+(xx)]=(cc)
 
   dx = fl->b.x - fl->a.x;
   ax = 2 * (dx<0 ? -dx : dx);
diff --git a/src/i_video.c b/src/i_video.c
index f37d5621..d8eb1792 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -480,7 +480,7 @@ void I_DynamicResolution(void)
     double actualpercent = actual / target;
 
     #define DRS_MIN_HEIGHT 400
-    #define DRS_DELTA 0.01
+    #define DRS_DELTA 0.1
     #define DRS_GREATER (1 + DRS_DELTA)
     #define DRS_LESS (1 - DRS_DELTA)
     #define DRS_STEP (SCREENHEIGHT / 2)
diff --git a/src/r_draw.c b/src/r_draw.c
index d1df014d..78b1818f 100644
--- a/src/r_draw.c
+++ b/src/r_draw.c
@@ -896,7 +896,7 @@ void R_FillBackScreen (void)
   // Allocate the background buffer if necessary
   if (background_buffer == NULL)
   {
-    int size = video.width * video.height;
+    int size = video.pitch * video.height;
     background_buffer = Z_Malloc(size * sizeof(*background_buffer), PU_STATIC, NULL);
   }
 
diff --git a/src/v_video.c b/src/v_video.c
index 987ee59f..7ff20efd 100644
--- a/src/v_video.c
+++ b/src/v_video.c
@@ -920,7 +920,7 @@ void V_PutBlock(int x, int y, int width, int height, byte *src)
 
 void V_ShadeScreen(void)
 {
-  int y;
+  int x, y;
   byte *dest = dest_screen;
   const int targshade = 20, step = 2;
   static int oldtic = -1;
@@ -932,9 +932,13 @@ void V_ShadeScreen(void)
     screenshade = 0;
   }
 
-  for (y = 0; y < video.width * video.height; y++)
+  for (y = 0; y < video.height; y++)
   {
-    dest[y] = colormaps[0][screenshade * 256 + dest[y]];
+    for (x = 0; x < video.width; x++)
+    {
+      dest[x] = colormaps[0][screenshade * 256 + dest[x]];
+    }
+    dest += linesize;
   }
 
   if (screenshade < targshade && gametic != oldtic)

From d38fd80fed896e7ae7e07e7e72b10e2a4262dfd2 Mon Sep 17 00:00:00 2001
From: Roman Fomin <rfomin@gmail.com>
Date: Fri, 22 Dec 2023 17:54:42 +0700
Subject: [PATCH 4/5] fix 21:9 aspect ratio, tweak DRS parameters

---
 src/i_video.c | 109 ++++++++++++++++++++++++++++++++------------------
 1 file changed, 71 insertions(+), 38 deletions(-)

diff --git a/src/i_video.c b/src/i_video.c
index d8eb1792..9c78688c 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -85,6 +85,7 @@ static SDL_Rect blit_rect = {0};
 
 static int window_x, window_y;
 static int actualheight;
+static int unscaled_actualheight;
 
 static int native_width;
 static int native_height;
@@ -467,6 +468,9 @@ static void ResetLogicalSize(void);
 
 void I_DynamicResolution(void)
 {
+    static int frame_counter;
+    static double averagepercent;
+
     if (resolution_mode != RES_DRS || frametime_withoutpresent == 0 ||
         frametime_withoutpresent > 1000000 / 15)
     {
@@ -480,7 +484,7 @@ void I_DynamicResolution(void)
     double actualpercent = actual / target;
 
     #define DRS_MIN_HEIGHT 400
-    #define DRS_DELTA 0.1
+    #define DRS_DELTA 0.01
     #define DRS_GREATER (1 + DRS_DELTA)
     #define DRS_LESS (1 - DRS_DELTA)
     #define DRS_STEP (SCREENHEIGHT / 2)
@@ -488,14 +492,17 @@ void I_DynamicResolution(void)
     int newheight = 0;
     int oldheight = video.height;
 
+    frame_counter++;
+    averagepercent = (averagepercent + actualpercent) / frame_counter;
+
     if (actualpercent > DRS_GREATER)
     {
         double reduction = (actualpercent - DRS_GREATER ) * 0.2;
         newheight = (int)MAX(DRS_MIN_HEIGHT, oldheight - oldheight * reduction);
     }
-    else if (actualpercent < DRS_LESS)
+    else if (averagepercent < DRS_LESS && frame_counter > targetrefresh)
     {
-        double addition = (DRS_LESS - actualpercent) * 0.25;
+        double addition = (DRS_LESS - averagepercent) * 0.25;
         newheight = (int)MIN(native_height_adjusted, oldheight + oldheight * addition);
     }
     else
@@ -503,6 +510,8 @@ void I_DynamicResolution(void)
         return;
     }
 
+    frame_counter = 0;
+
     int mul = (newheight + (DRS_STEP - 1)) / DRS_STEP; // integer round
 
     newheight = mul * DRS_STEP;
@@ -570,13 +579,13 @@ void I_FinishUpdate(void)
 
     I_DrawDiskIcon();
 
+    UpdateRender();
+
     if (frametime_start)
     {
         frametime_withoutpresent = I_GetTimeUS() - frametime_start;
     }
 
-    UpdateRender();
-
     SDL_RenderPresent(renderer);
 
     I_RestoreDiskBackground();
@@ -953,20 +962,15 @@ static void I_GetWindowPosition(int *x, int *y, int w, int h)
     }
 }
 
-static void ResetResolution(int height)
+static double CurrentAspectRatio(void)
 {
     int w, h;
 
-    int unscaled_ah = use_aspect ? ACTUALHEIGHT : SCREENHEIGHT;
-
-    actualheight = use_aspect ? (int)(height * 1.2) : height;
-    video.height = height;
-
     switch (widescreen)
     {
         case RATIO_ORIG:
             w = SCREENWIDTH;
-            h = unscaled_ah;
+            h = unscaled_actualheight;
             break;
         case RATIO_MATCH_SCREEN:
             w = native_width;
@@ -997,9 +1001,19 @@ static void ResetResolution(int height)
         aspect_ratio = 2.4;
     }
 
-    video.unscaledw = (int)(unscaled_ah * aspect_ratio);
+    return aspect_ratio;
+}
 
-    double vertscale = (double)actualheight / (double)unscaled_ah;
+static void ResetResolution(int height)
+{
+    double aspect_ratio = CurrentAspectRatio();
+
+    actualheight = use_aspect ? (int)(height * 1.2) : height;
+    video.height = height;
+
+    video.unscaledw = (int)(unscaled_actualheight * aspect_ratio);
+
+    double vertscale = (double)actualheight / (double)unscaled_actualheight;
     video.width = (int)(video.unscaledw * vertscale);
     video.width = (video.width + 1) & ~1;
 
@@ -1015,7 +1029,7 @@ static void ResetResolution(int height)
 
     I_InitDiskFlash();
 
-    I_Printf(VB_DEBUG, "ResetResolution: %dx%d", video.width, actualheight);
+    I_Printf(VB_DEBUG, "ResetResolution: %dx%d", video.width, video.height);
 }
 
 static void CreateUpscaledTexture(boolean force)
@@ -1149,6 +1163,30 @@ void I_ResetTargetRefresh(void)
 static void I_InitVideoParms(void)
 {
     int p, tmp_scalefactor;
+    SDL_DisplayMode mode;
+
+    if (SDL_GetCurrentDisplayMode(video_display, &mode))
+    {
+        I_Error("Error getting display mode: %s", SDL_GetError());
+    }
+
+    native_width = mode.w;
+    native_height = mode.h;
+    native_refresh_rate = mode.refresh_rate;
+
+    widescreen = default_widescreen;
+
+    double aspect_ratio = CurrentAspectRatio();
+    double native_aspect_ratio = (double)native_width / (double)native_height;
+
+    if (widescreen && native_aspect_ratio < aspect_ratio)
+    {
+        native_height = (int)(native_width / aspect_ratio);
+    }
+
+    native_height_adjusted = use_aspect ? (int)(native_height / 1.2) : native_height;
+
+    unscaled_actualheight = use_aspect ? ACTUALHEIGHT: SCREENHEIGHT;
 
     I_ResetInvalidDisplayIndex();
     resolution_mode = default_resolution_mode;
@@ -1326,46 +1364,44 @@ static void I_InitGraphicsMode(void)
 
 static int CurrentResolutionMode(void)
 {
+    int height;
+
     switch (resolution_mode)
     {
         case RES_ORIGINAL:
-            return SCREENHEIGHT;
+            height = SCREENHEIGHT;
+            break;
         case RES_DOUBLE:
-            return SCREENHEIGHT * 2;
+            height = SCREENHEIGHT * 2;
+            break;
         case RES_TRIPLE:
-            return SCREENHEIGHT * 3;
-        case RES_DRS:
-            return native_height_adjusted;
+            height = SCREENHEIGHT * 3;
+            break;
         default:
-            return native_height_adjusted;
+            height = native_height_adjusted;
+            break;
     }
+
+    if (height > native_height_adjusted)
+    {
+        height = native_height_adjusted;
+    }
+
+    return height;
 }
 
 static void CreateSurfaces(void)
 {
     int w, h;
-    SDL_DisplayMode mode;
-
-    if (SDL_GetCurrentDisplayMode(video_display, &mode))
-    {
-        I_Error("Error getting display mode: %s", SDL_GetError());
-    }
-
-    native_width = mode.w;
-    native_height = mode.h;
-    native_refresh_rate = mode.refresh_rate;
 
     w = native_width;
-    h = use_aspect ? (int)(native_height / 1.2) : native_height;
-
-    native_height_adjusted = h;
+    h = native_height_adjusted;
 
     // [FG] For performance reasons, SDL2 insists that the screen pitch, i.e.
     // the *number of bytes* that one horizontal row of pixels occupy in
     // memory, must be a multiple of 4.
 
     w = (w + 3) & ~3;
-    h = (h + 3) & ~3;
 
     video.pitch = w;
 
@@ -1384,9 +1420,6 @@ static void CreateSurfaces(void)
     I_VideoBuffer = screenbuffer->pixels;
     V_RestoreBuffer();
 
-    // Clear the screen to black.
-    memset(I_VideoBuffer, 0, w * h * sizeof(*I_VideoBuffer));
-
     if (argbbuffer != NULL)
     {
         SDL_FreeSurface(argbbuffer);

From 472aeb099699ca376c0e125992191b8a328c16ee Mon Sep 17 00:00:00 2001
From: Roman Fomin <rfomin@gmail.com>
Date: Sat, 23 Dec 2023 14:57:40 +0700
Subject: [PATCH 5/5] add comments

---
 src/i_video.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/i_video.c b/src/i_video.c
index 9c78688c..44b3dbf5 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -472,6 +472,7 @@ void I_DynamicResolution(void)
     static double averagepercent;
 
     if (resolution_mode != RES_DRS || frametime_withoutpresent == 0 ||
+        // Skip if frame time is too long (e.g. window event).
         frametime_withoutpresent > 1000000 / 15)
     {
         return;
@@ -487,11 +488,15 @@ void I_DynamicResolution(void)
     #define DRS_DELTA 0.01
     #define DRS_GREATER (1 + DRS_DELTA)
     #define DRS_LESS (1 - DRS_DELTA)
+    // 100px step to make scaling artefacts less noticeable.
     #define DRS_STEP (SCREENHEIGHT / 2)
 
     int newheight = 0;
     int oldheight = video.height;
 
+    // Decrease the resolution quickly, increase only when the average frame
+    // time is stable for the `targetrefresh` number of frames.
+
     frame_counter++;
     averagepercent = (averagepercent + actualpercent) / frame_counter;
 
@@ -1013,6 +1018,11 @@ static void ResetResolution(int height)
 
     video.unscaledw = (int)(unscaled_actualheight * aspect_ratio);
 
+    // Unscaled widescreen 16:9 resolution truncates to 426x240, which is not
+    // quite 16:9. To avoid visual instability, we calculate the scaled width
+    // without the actual aspect ratio. For example, at 1280x720 we get
+    // 1278x720.
+
     double vertscale = (double)actualheight / (double)unscaled_actualheight;
     video.width = (int)(video.unscaledw * vertscale);
     video.width = (video.width + 1) & ~1;