Fix an off-by-less-than-one issue in bitmap_double_mult_inside()

This was sometimes causing an integer scaled mode (ie: 4×) to be
reduced to very slightly less than that (ie: 3.996255×), making the
window one pixel smaller than it was supposed to be due to integer
truncation.

This could result in being unable to increase the window size using
the Alt+Right-Arrow shortcut and could make new windows one full
size smaller than they needed to be (such as C64 windows).

While we're here, fix the SDL and X11 outputs to trust what
bitmap_drv_init_mode() does.  It was fixed when GDI mode was being
written, but the other drivers weren't updated to take advantage of
that.

Should resolve issue 156 reported by DigitalMan

src/conio/bitmap_con.c

@@ -1711,15 +1711,29 @@ bitmap_double_mult_inside(int maxwidth, int maxheight)
 	double mult = 1.0;
 	double wmult = 1.0;
 	double hmult = 1.0;
+	int wmw, wmh;
+	int hmw, hmh;
 	int w, h;
 
 	bitmap_get_scaled_win_size_nomax(1.0, &w, &h);
 	wmult = (double)maxwidth / w;
 	hmult = (double)maxheight / h;
-	if (wmult < hmult)
+	bitmap_get_scaled_win_size_nomax(wmult, &wmw, &wmh);
+	bitmap_get_scaled_win_size_nomax(hmult, &hmw, &hmh);
+	if (wmult < hmult) {
+		if (hmw <= maxwidth && hmh <= maxheight)
+			mult = hmult;
+		else
+			mult = wmult;
+	}
+	else if(hmult < wmult) {
+		if (wmw <= maxwidth && wmh <= maxheight)
 			mult = wmult;
 		else
 			mult = hmult;
+	}
+	else
+		mult = hmult;
 	// TODO: Allow below 1.0?
 	if (mult < 1.0)
 		mult = 1.0;

src/conio/sdl_con.c

@@ -372,21 +372,10 @@ static int sdl_init_mode(int mode, bool init)
 	}
 	bitmap_drv_init_mode(mode, &bitmap_width, &bitmap_height, w, h);
 	if (ciolib_initial_scaling < 1.0) {
-		if (w != 0 && h != 0) {
-			w *= ciolib_initial_scaling;
-			h *= ciolib_initial_scaling;
-			ciolib_initial_scaling = bitmap_double_mult_inside(w, h);
-		}
-		if (ciolib_initial_scaling < 1.0) {
+		ciolib_initial_scaling = vstat.scaling;
+		if (ciolib_initial_scaling < 1.0)
 			ciolib_initial_scaling = 1.0;
 	}
-	}
-	if (init) {
-		internal_scaling = (ciolib_initial_scaling_type == CIOLIB_SCALING_INTERNAL);
-		if (ciolib_initial_scaling) {
-			bitmap_get_scaled_win_size(ciolib_initial_scaling, &vstat.winwidth, &vstat.winheight, 0, 0);
-		}
-	}
 	pthread_mutex_lock(&sdl_mode_mutex);
 	sdl_mode = true;
 	pthread_mutex_unlock(&sdl_mode_mutex);

src/conio/x_events.c

@@ -1227,17 +1227,19 @@ static void resize_window()
 static void init_mode_internal(int mode)
 {
 	int mw, mh;
-	int ow, oh;
 
 	x11_get_maxsize(&mw, &mh);
 	free_last();
 	pthread_mutex_lock(&vstatlock);
-	ow = vstat.winwidth;
-	oh = vstat.winheight;
+	double os = vstat.scaling;
+	int ow = vstat.winwidth;
+	int oh = vstat.winheight;
 	bitmap_drv_init_mode(mode, NULL, NULL, mw, mh);
+	// TODO: This hacks the right values into the wrong places so resize_window() fixes them.
+	x_cvstat.scaling = vstat.scaling;
+	vstat.scaling = os;
 	vstat.winwidth = ow;
 	vstat.winheight = oh;
-	vstat.scaling = bitmap_double_mult_inside(ow, oh);
 	pthread_mutex_unlock(&vstatlock);
 	resize_window();
 	pthread_mutex_lock(&vstatlock);