Allow scrolling through recipe handlers (#379)

In addition to scrolling through all recipes of a single handler, you
can now scroll through all the recipe handlers while hovering over the
handler tab bar (or anywhere in the recipe area while holding left
shift).

src/main/java/codechicken/nei/recipe/GuiRecipe.java

@@ -388,6 +388,8 @@ public abstract class GuiRecipe<H extends IRecipeHandler> extends GuiContainer i
         // the value of the height field will be different from in other mouseover methods, which
         // could be confusing...
 
+        if (recipeTabs.mouseScrolled(i)) return;
+
         for (int recipe : getRecipeIndices()) if (handler.mouseScrolled(this, i, recipe)) return;
 
         if (new Rectangle(guiLeft, guiTop, xSize, ySize).contains(GuiDraw.getMousePosition())) {
@@ -462,11 +464,11 @@ public abstract class GuiRecipe<H extends IRecipeHandler> extends GuiContainer i
         if (page < 0) page = (handler.numRecipes() - 1) / getRecipesPerPage();
     }
 
-    private void nextType() {
+    protected void nextType() {
         setRecipePage(++recipetype);
     }
 
-    private void prevType() {
+    protected void prevType() {
         setRecipePage(--recipetype);
     }
 

src/main/java/codechicken/nei/recipe/GuiRecipeTabs.java

@@ -1,9 +1,13 @@
 package codechicken.nei.recipe;
 
+import static codechicken.lib.gui.GuiDraw.getMousePosition;
+
 import java.awt.*;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.lwjgl.input.Keyboard;
+
 import codechicken.nei.Button;
 import codechicken.nei.NEIClientConfig;
 import codechicken.nei.NEIClientUtils;
@@ -192,4 +196,22 @@ public class GuiRecipeTabs {
         }
         return false;
     }
+
+    protected boolean mouseScrolled(int i) {
+        Point mPos = getMousePosition();
+
+        // Switch recipe handler tabs if either left shift is held or the tab
+        // bar is enable and the mouse cursor is positioned over said tab bar.
+        if (Keyboard.isKeyDown(Keyboard.KEY_LSHIFT)
+                || (NEIClientConfig.areJEIStyleTabsVisible() && (mPos.x >= area.x && mPos.x <= (area.x + area.width)
+                        && mPos.y >= area.y
+                        && mPos.y <= (area.y + area.height)))) {
+            if (i < 0) guiRecipe.nextType();
+            else guiRecipe.prevType();
+
+            return true;
+        }
+
+        return false;
+    }
 }