commit f5b04622c28e4af5c5bb93dfd10a7f1fe1312ec4
Author:     Simon Howard <fraggle@soulsphere.org>
AuthorDate: Sat Jul 23 17:50:56 2016 -0400
Commit:     Simon Howard <fraggle@soulsphere.org>
CommitDate: Sat Jul 23 17:50:56 2016 -0400

    textscreen: Fix rendering when using a tiling WM.

    When using a tiling window manager, the window dimensions as passed
    to SDL_CreateWindow() can potentially be ignored, and we can end up
    with a different window size even though we didn't ask for the window
    to be resizeable.

    In this situation, we were scaling the textscreen image to always fill
    the window, regardless of size or aspect ratio. This led to some nasty
    looking, distorted views in some cases. Instead, always render the
    textscreen image at the intended size and center the image within the
    window if it is not the requested size.
---
 textscreen/txt_sdl.c | 66 +++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 50 insertions(+), 16 deletions(-)

diff --git a/textscreen/txt_sdl.c b/textscreen/txt_sdl.c
index 9c95454a..57d90644 100644
--- a/textscreen/txt_sdl.c
+++ b/textscreen/txt_sdl.c
@@ -55,6 +55,10 @@ static unsigned char *screendata;
 static SDL_Renderer *renderer;
 static int key_mapping = 1;

+// Dimensions of the screen image in screen coordinates (not pixels); this
+// is the value that was passed to SDL_CreateWindow().
+static int screen_image_w, screen_image_h;
+
 static TxtSDLEventCallbackFunc event_callback;
 static void *event_callback_data;

@@ -244,7 +248,6 @@ static void ChooseFont(void)

 int TXT_Init(void)
 {
-    int window_w, window_h;
     int flags = 0;

     if (SDL_Init(SDL_INIT_VIDEO) < 0)
@@ -254,8 +257,8 @@ int TXT_Init(void)

     ChooseFont();

-    window_w = TXT_SCREEN_W * font->w;
-    window_h = TXT_SCREEN_H * font->h;
+    screen_image_w = TXT_SCREEN_W * font->w;
+    screen_image_h = TXT_SCREEN_H * font->h;

     // If highdpi_font is selected, try to initialize high dpi rendering.
     if (font == &highdpi_font)
@@ -265,7 +268,7 @@ int TXT_Init(void)

     TXT_SDLWindow =
         SDL_CreateWindow("", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
-                         window_w, window_h, flags);
+                         screen_image_w, screen_image_h, flags);

     if (TXT_SDLWindow == NULL)
         return 0;
@@ -281,10 +284,13 @@ int TXT_Init(void)
         int render_w, render_h;

         if (SDL_GetRendererOutputSize(renderer, &render_w, &render_h) == 0
-         && render_w == TXT_SCREEN_W * large_font.w
-         && render_h == TXT_SCREEN_H * large_font.h)
+         && render_w >= TXT_SCREEN_W * large_font.w
+         && render_h >= TXT_SCREEN_H * large_font.h)
         {
             font = &large_font;
+            // Note that we deliberately do not update screen_image_{w,h}
+            // since these are the dimensions of textscreen image in screen
+            // coordinates, not pixels.
         }
     }

@@ -411,6 +417,17 @@ static int LimitToRange(int val, int min, int max)
     }
 }

+static void GetDestRect(SDL_Rect *rect)
+{
+    int w, h;
+
+    SDL_GetRendererOutputSize(renderer, &w, &h);
+    rect->x = (w - screenbuffer->w) / 2;
+    rect->y = (h - screenbuffer->h) / 2;
+    rect->w = screenbuffer->w;
+    rect->h = screenbuffer->h;
+}
+
 void TXT_UpdateScreenArea(int x, int y, int w, int h)
 {
     SDL_Texture *screentx;
@@ -434,11 +451,6 @@ void TXT_UpdateScreenArea(int x, int y, int w, int h)
         }
     }

-    rect.x = x * font->w;
-    rect.y = y * font->h;
-    rect.w = (x_end - x) * font->w;
-    rect.h = (y_end - y) * font->h;
-
     SDL_UnlockSurface(screenbuffer);

     SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "linear");
@@ -448,7 +460,8 @@ void TXT_UpdateScreenArea(int x, int y, int w, int h)
     screentx = SDL_CreateTextureFromSurface(renderer, screenbuffer);

     SDL_RenderClear(renderer);
-    SDL_RenderCopy(renderer, screentx, NULL, NULL);
+    GetDestRect(&rect);
+    SDL_RenderCopy(renderer, screentx, NULL, &rect);
     SDL_RenderPresent(renderer);

     SDL_DestroyTexture(screentx);
@@ -462,15 +475,36 @@ void TXT_UpdateScreen(void)
 void TXT_GetMousePosition(int *x, int *y)
 {
     int window_w, window_h;
+    int origin_x, origin_y;

     SDL_GetMouseState(x, y);

     // Translate mouse position from 'pixel' position into character position.
-    // Note that font->{w,h} are deliberately not used in this calculation, as
-    // that would break when using highdpi (OS X retina display).
+    // We are working here in screen coordinates and not pixels, since this is
+    // what SDL_GetWindowSize() returns; we must calculate and subtract the
+    // origin position since we center the image within the window.
     SDL_GetWindowSize(TXT_SDLWindow, &window_w, &window_h);
-    *x = (*x * TXT_SCREEN_W) / window_w;
-    *y = (*y * TXT_SCREEN_H) / window_h;
+    origin_x = (window_w - screen_image_w) / 2;
+    origin_y = (window_h - screen_image_h) / 2;
+    *x = ((*x - origin_x) * TXT_SCREEN_W) / screen_image_w;
+    *y = ((*y - origin_y) * TXT_SCREEN_H) / screen_image_h;
+
+    if (*x < 0)
+    {
+        *x = 0;
+    }
+    else if (*x >= TXT_SCREEN_W)
+    {
+        *x = TXT_SCREEN_W - 1;
+    }
+    if (*y < 0)
+    {
+        *y = 0;
+    }
+    else if (*y >= TXT_SCREEN_H)
+    {
+        *y = TXT_SCREEN_H - 1;
+    }
 }

 //