Add a "previous page" option to the levels list

This makes it more convenient if you have a large levels directory, as
some people in the VVVVVV custom levels community do.

On the first page, this option will change to be "last page" instead.

Since the addition of another menu option pushes up the list of levels
too close to the selected level data itself, I've had to move the list
of levels down by 4 pixels (but "next page"/"previous page"/"return to
menu" are still in their same position).

This feature was already added to VCE but hasn't been upstreamed until
now.

desktop_version/src/Game.cpp

@@ -6690,6 +6690,14 @@ void Game::createmenu( enum Menu::MenuName t, bool samemenu/*= false*/ )
             {
                 option("first page");
             }
+            if (levelpage == 0)
+            {
+                option("last page");
+            }
+            else
+            {
+                option("previous page");
+            }
             option("return to menu");
 
             menuxoff = -90;

desktop_version/src/Graphics.cpp

@@ -1129,7 +1129,7 @@ void Graphics::drawlevelmenu( int cr, int cg, int cb, int division /*= 30*/ )
     {
         if ((int) i == game.currentmenuoption)
         {
-          if(game.menuoptions.size()-i<=2){
+          if(game.menuoptions.size()-i<=3){
             //Draw it highlighted
             if (game.menuoptions[i].active)
             {
@@ -1152,20 +1152,20 @@ void Graphics::drawlevelmenu( int cr, int cg, int cb, int division /*= 30*/ )
                 std::string tempstring = game.menuoptions[i].text;
                 std::transform(tempstring.begin(), tempstring.end(),tempstring.begin(), ::toupper);
                 tempstring = std::string("[ ") + tempstring + std::string(" ]");
-                Print(110 + (i * division) - 16 +game.menuxoff, 140 + (i * 12) +game.menuyoff, tempstring, cr, cg, cb);
+                Print(110 + (i * division) - 16 +game.menuxoff, 144 + (i * 12) +game.menuyoff, tempstring, cr, cg, cb);
             }
             else
             {
                 std::string tempstring = game.menuoptions[i].text;
                 tempstring = "[ " + tempstring + " ]";
                 //Draw it in gray
-                Print(110 + (i * division) - 16 +game.menuxoff, 140 + (i * 12)+game.menuyoff, tempstring, 128, 128, 128);
+                Print(110 + (i * division) - 16 +game.menuxoff, 144 + (i * 12)+game.menuyoff, tempstring, 128, 128, 128);
             }
           }
         }
         else
         {
-          if(game.menuoptions.size()-i<=2){
+          if(game.menuoptions.size()-i<=3){
             //Draw it normally
             if (game.menuoptions[i].active)
             {
@@ -1180,12 +1180,12 @@ void Graphics::drawlevelmenu( int cr, int cg, int cb, int division /*= 30*/ )
             //Draw it normally
             if (game.menuoptions[i].active)
             {
-                Print(110 + (i * division) +game.menuxoff, 140 + (i * 12)+game.menuyoff, game.menuoptions[i].text, cr, cg, cb);
+                Print(110 + (i * division) +game.menuxoff, 144 + (i * 12)+game.menuyoff, game.menuoptions[i].text, cr, cg, cb);
             }
             else
             {
                 //Draw it in gray
-                Print(110 + (i * division) +game.menuxoff, 140 + (i * 12)+game.menuyoff, game.menuoptions[i].text, 128, 128, 128);
+                Print(110 + (i * division) +game.menuxoff, 144 + (i * 12)+game.menuyoff, game.menuoptions[i].text, 128, 128, 128);
             }
           }
         }

desktop_version/src/Input.cpp

@@ -199,6 +199,17 @@ void menuactionpress()
             game.returnmenu();
             map.nexttowercolour();
         }else if(game.currentmenuoption==(int)game.menuoptions.size()-2){
+            //previous page
+            music.playef(11);
+            if(game.levelpage==0){
+                game.levelpage=(ed.ListOfMetaData.size()-1)/8;
+            }else{
+                game.levelpage--;
+            }
+            game.createmenu(Menu::levellist, true);
+            game.currentmenuoption=game.menuoptions.size()-2;
+            map.nexttowercolour();
+        }else if(game.currentmenuoption==(int)game.menuoptions.size()-3){
             //next page
             music.playef(11);
             if((size_t) ((game.levelpage*8)+8) >= ed.ListOfMetaData.size()){
@@ -207,7 +218,7 @@ void menuactionpress()
                 game.levelpage++;
             }
             game.createmenu(Menu::levellist, true);
-            game.currentmenuoption=game.menuoptions.size()-2;
+            game.currentmenuoption=game.menuoptions.size()-3;
             map.nexttowercolour();
         }else{
             //Ok, launch the level!

desktop_version/src/Render.cpp

@@ -46,8 +46,8 @@ void menurender()
       }
       int tmp=game.currentmenuoption+(game.levelpage*8);
       if(tmp>=0 && tmp < (int) ed.ListOfMetaData.size()){ // FIXME: size_t/int! -flibit
-        //Don't show next page or return to menu options here!
+        //Don't show next/previous page or return to menu options here!
-        if(game.menuoptions.size() - game.currentmenuoption<=2){
+        if(game.menuoptions.size() - game.currentmenuoption<=3){
 
         }else{
           graphics.bigprint( -1, 15, ed.ListOfMetaData[tmp].title, tr, tg, tb, true);