Move display stuff in a dedicated source file

The display ratio is computed with the user's screen. It's no longer a
static value.

It must be improved in order to fix the ratio according to screen
changes.

src/def.h

@@ -22,18 +22,11 @@
 
 #include <SDL2/SDL_stdinc.h>
 
+#include "display.h"
+
 // clang-format off
 #define _INTRO          true    // true for init screen
 
-#define SCRNUM          16
-#define SCRDEN          9
-#define SCRFACTOR       SCRNUM / SCRDEN
-#define LXLOGIC         640
-#define LYLOGIC         480
-#define LXIMAGE         (LYLOGIC * SCRFACTOR + (LYLOGIC * SCRFACTOR) % 2) // window size
-#define LYIMAGE         LYLOGIC
-#define LXOFFSET        ((LXIMAGE - LXLOGIC) / 2)
-
 #define POSDRAWX        144     // draw surface
 #define POSDRAWY        15
 #define DIMDRAWX        (LXIMAGE - (LXLOGIC - LYLOGIC))

src/display.cxx

@@ -0,0 +1,71 @@
+
+#include <SDL2/SDL_video.h>
+
+#include "blupi.h"
+#include "display.h"
+
+#define SCRNUM 16
+#define SCRDEN 9
+#define SCRFACTOR SCRNUM / SCRDEN
+
+Display::Display ()
+{
+  this->width  = 0;
+  this->height = 0;
+}
+
+void
+Display::readDisplaySize ()
+{
+  SDL_DisplayMode displayMode;
+  SDL_GetWindowDisplayMode (g_window, &displayMode);
+  this->width  = displayMode.w;
+  this->height = displayMode.h;
+}
+
+Display &
+Display::getDisplay ()
+{
+  static bool    init = false;
+  static Display display;
+
+  if (!init)
+  {
+    display.readDisplaySize ();
+    init = true;
+  }
+
+  return display;
+}
+
+double
+Display::getRatio ()
+{
+  return this->width / this->height;
+}
+
+Sint32
+Display::getWidth ()
+{
+  return (
+    this->getLogicHeight () * SCRFACTOR +
+    (this->getLogicHeight () * SCRFACTOR) % 2);
+}
+
+Sint32
+Display::getHeight ()
+{
+  return this->getLogicHeight ();
+}
+
+Sint32
+Display::getLogicWidth ()
+{
+  return 640;
+}
+
+Sint32
+Display::getLogicHeight ()
+{
+  return 480;
+}

src/display.h

@@ -0,0 +1,31 @@
+
+#pragma once
+
+#include "SDL2/SDL_stdinc.h"
+
+class Display
+{
+private:
+	Sint32 width;
+	Sint32 height;
+
+private:
+  Display ();
+
+  void readDisplaySize ();
+
+public:
+  static Display & getDisplay ();
+
+  double getRatio ();
+  Sint32 getWidth ();
+  Sint32 getHeight ();
+  Sint32 getLogicWidth ();
+  Sint32 getLogicHeight ();
+};
+
+#define LXLOGIC (Display::getDisplay ().getLogicWidth ())
+#define LYLOGIC (Display::getDisplay ().getLogicHeight ())
+#define LXIMAGE (Display::getDisplay ().getWidth ())
+#define LYIMAGE (Display::getDisplay ().getHeight ())
+#define LXOFFSET ((LXIMAGE - LXLOGIC) / 2)