espie@ added feature

Index: platform/x11/pdfapp.c
--- platform/x11/pdfapp.c.orig
+++ platform/x11/pdfapp.c
@@ -175,11 +175,21 @@ static void pdfapp_sleep(int ms)
 static void pdfapp_showpage(pdfapp_t *app, int loadpage, int drawpage, int repaint, int transition, int searching);
 
 static const int zoomlist[] = {
-	18, 24, 36, 54, 72, 96, 120, 144, 180,
-	216, 288, 360, 432, 504, 576, 648, 720,
-	792, 864, 936, 1008, 1080, 1152
+	18, 21, 24, 30, 36, 44, 54, 62, 72, 83, 96, 107, 120, 131, 144, 160, 180, 197,
+	216, 250, 288, 322, 360, 394, 432, 466, 504, 538, 576, 610, 648, 682, 720, 754,
+	792, 826, 864, 898, 936, 970, 1008, 1042, 1080, 1114, 1152
 };
 
+static int fine_zoom_in(int oldres)
+{
+	return oldres+1;
+}
+
+static int fine_zoom_out(int oldres)
+{
+	return oldres-1;
+}
+
 static int zoom_in(int oldres)
 {
 	int i;
@@ -1642,6 +1652,7 @@ key_rewritten:
 			app->pageno++;
 		break;
 
+	case '\b': /* backspace */
 	case 'b':
 		{
 			int number = 1;
@@ -1688,7 +1699,7 @@ key_rewritten:
 				{
 					if (app->imgw + app->panx <= app->winw + app->imgw/20)
 					{
-						if (app->pageno + 1 <= app->pagecount)
+						if (app->pageno <= app->pagecount)
 						{
 							app->panx = 0;
 							app->pany = 0;
@@ -1800,9 +1811,9 @@ static void handlescroll(pdfapp_t *app, int modifiers,
 	{
 		/* zoom in/out if ctrl is pressed */
 		if (dir > 0)
-			app->resolution = zoom_in(app->resolution);
+			app->resolution = ((modifiers & (1<<0)) ? fine_zoom_in : zoom_in)(app->resolution);
 		else
-			app->resolution = zoom_out(app->resolution);
+			app->resolution = ((modifiers & (1<<0)) ? fine_zoom_out : zoom_out)(app->resolution);
 		if (app->resolution > MAXRES)
 			app->resolution = MAXRES;
 		if (app->resolution < MINRES)