Improve ScrollArea (#325)

This PR adds a collection of small improvements and preparation for
freezing the first column (tab/page name column) of the SummaryView
ScrollArea. This is working almost fully working and I am using it
locally all the time: the only left-over issue is that the the
scrollbars are disappeared. (so the UX is a little off 😉 )
I pushed [this 'freeze-first-summary-column'
branch](https://github.com/veger/yafc-ce/tree/freeze-first-summary-column)
with this fix to my own fork, so it is be more publicly available, until
I (or someone) is able to fix the missing scrollbars, so we can actually
merge!

---

I have these changes for ages in my local repo, and I do think these are
suitable on their own to be committed. It will help me (re)fixing them
on style changes or other code changes.

Each change is a separate commit (as I think we should keep them), so it
is fairly easy if we do not like one of them (then I'll move back to my
[freeze-first-summary-column](https://github.com/veger/yafc-ce/tree/freeze-first-summary-column)
where most of them are required to make this feature work.

For testing I opened up YAFC and clicked around a bit, all still seem to
be working/rendering the same, except:
* empty Summary rows (now) properly render
(8930a9c)
* scrolling still works (without the fallback, see
b6e04c2 and
52491b1)

Yafc.UI/ImGui/ScrollArea.cs

@@ -24,7 +24,7 @@ public abstract class Scrollable(bool vertical, bool horizontal, bool collapsibl
 
     protected abstract void PositionContent(ImGui gui, Rect viewport);
 
-    /// <param name="availableHeight">Available height without in parent context for the Scrollable</param>
+    /// <param name="availableHeight">Available height in parent context for the Scrollable</param>
     public void Build(ImGui gui, float availableHeight, bool useBottomPadding = false) {
         this.gui = gui;
         var rect = gui.statePosition;
@@ -75,14 +75,11 @@ public void Build(ImGui gui, float availableHeight, bool useBottomPadding = fals
         }
 
         if (gui.action == ImGuiAction.MouseScroll) {
-            if (gui.ConsumeEvent(rect)) {
-                if (vertical && (!horizontal || !InputSystem.Instance.control)) {
-                    scrollY += gui.actionParameter * 3f;
-                }
-                else {
-                    scrollX += gui.actionParameter * 3f;
-                }
-            }
+            if (vertical && !InputSystem.Instance.control && gui.ConsumeEvent(rect))
+                scrollY += gui.actionParameter * 3f;
+
+            else if (horizontal && InputSystem.Instance.control && gui.ConsumeEvent(rect))
+                scrollX += gui.actionParameter * 3f;
         }
         else {
             if (horizontal && maxScroll.X > 0f) {
@@ -150,47 +147,83 @@ public float scrollX {
 
     ///<summary>This method is called when the required area of the <see cref="Scrollable"/> for the provided <paramref name="width"/> is needed.</summary>
     /// <returns>The required area of the contents of the <see cref="Scrollable"/>.</returns>
-    protected abstract Vector2 MeasureContent(float width, ImGui gui);
+    public abstract Vector2 MeasureContent(float width, ImGui gui);
 
     public bool KeyDown(SDL.SDL_Keysym key) {
         bool ctrl = InputSystem.Instance.control;
         bool shift = InputSystem.Instance.shift;
 
         switch ((ctrl, shift, key.scancode)) {
             case (false, false, SDL.SDL_Scancode.SDL_SCANCODE_UP):
+                if (!vertical) {
+                    return false;
+                }
                 scrollY -= 3;
                 return true;
-            case (true, false, SDL.SDL_Scancode.SDL_SCANCODE_UP):
-                scrollY = 0; // ctrl+up = home
+            case (true, false, SDL.SDL_Scancode.SDL_SCANCODE_UP): // ctrl+up = home
+                if (!vertical) {
+                    return false;
+                }
+                scrollY = 0;
                 return true;
             case (false, false, SDL.SDL_Scancode.SDL_SCANCODE_DOWN):
+                if (!vertical) {
+                    return false;
+                }
                 scrollY += 3;
                 return true;
-            case (true, false, SDL.SDL_Scancode.SDL_SCANCODE_DOWN):
-                scrollY = maxScroll.Y; // ctrl+down = end
+            case (true, false, SDL.SDL_Scancode.SDL_SCANCODE_DOWN): // ctrl+down = end
+                if (!vertical) {
+                    return false;
+                }
+                scrollY = maxScroll.Y;
                 return true;
             case (false, false, SDL.SDL_Scancode.SDL_SCANCODE_LEFT):
+                if (!horizontal) {
+                    return false;
+                }
                 scrollX -= 3;
                 return true;
-            case (true, false, SDL.SDL_Scancode.SDL_SCANCODE_LEFT):
+            case (true, false, SDL.SDL_Scancode.SDL_SCANCODE_LEFT): // ctrl+left = start of line
+                if (!horizontal) {
+                    return false;
+                }
                 scrollX = 0;
                 return true;
             case (false, false, SDL.SDL_Scancode.SDL_SCANCODE_RIGHT):
+                if (!horizontal) {
+                    return false;
+                }
                 scrollX += 3;
                 return true;
-            case (true, false, SDL.SDL_Scancode.SDL_SCANCODE_RIGHT):
+            case (true, false, SDL.SDL_Scancode.SDL_SCANCODE_RIGHT):  // ctrl+right = end of line
+                if (!horizontal) {
+                    return false;
+                }
                 scrollX = maxScroll.X;
                 return true;
             case (false, false, SDL.SDL_Scancode.SDL_SCANCODE_PAGEDOWN):
+                if (!vertical) {
+                    return false;
+                }
                 scrollY += contentRect.Height;
                 return true;
             case (false, false, SDL.SDL_Scancode.SDL_SCANCODE_PAGEUP):
+                if (!vertical) {
+                    return false;
+                }
                 scrollY -= contentRect.Height;
                 return true;
             case (false, false, SDL.SDL_Scancode.SDL_SCANCODE_HOME):
                 scrollY = 0;
+                if (!vertical) {
+                    return false;
+                }
                 return true;
             case (false, false, SDL.SDL_Scancode.SDL_SCANCODE_END):
+                if (!vertical) {
+                    return false;
+                }
                 scrollY = maxScroll.Y;
                 return true;
             default:
@@ -226,7 +259,8 @@ protected override void PositionContent(ImGui gui, Rect viewport) {
 
     public void RebuildContents() => contents.Rebuild();
 
-    protected override Vector2 MeasureContent(float width, ImGui gui) => contents.CalculateState(width, gui.pixelsPerUnit);
+    ///<summary>Calculates the content dimensions by (re)building the contents using <see cref="BuildContents"/></summary>
+    public override Vector2 MeasureContent(float width, ImGui gui) => contents.CalculateState(width, gui.pixelsPerUnit);
 }
 
 ///<summary>Area with scrollbars, which will be visible if it does not fit in the parent area in order to let the user fully view the content of the area.</summary>

Yafc/Widgets/DataGrid.cs

@@ -81,7 +81,7 @@ public virtual void BuildMenu(ImGui gui) { }
 
 public class DataGrid<TData> where TData : class {
     public readonly List<DataColumn<TData>> columns;
-    private readonly Padding innerPadding = new Padding(0.2f);
+    public static readonly Padding innerPadding = new Padding(0.2f);
     public float width { get; private set; }
     private readonly float spacing;
     private Vector2 buildingStart;

Yafc/Widgets/ImmediateWidgets.cs

@@ -250,7 +250,7 @@ public static void BuildInlineObjectListAndButtonWithNone<T>(this ImGui gui, ICo
     /// <param name="useScale">If <see langword="true"/>, this icon will be displayed at <see cref="ProjectPreferences.iconScale"/>, instead of at 100% scale.</param>
     public static Click BuildFactorioObjectWithAmount(this ImGui gui, FactorioObject? goods, DisplayAmount amount, ButtonDisplayStyle buttonDisplayStyle, TextBlockDisplayStyle? textDisplayStyle = null, ObjectTooltipOptions tooltipOptions = default) {
         textDisplayStyle ??= new(Alignment: RectAlignment.Middle);
-        using (gui.EnterFixedPositioning(3f, 3f, default)) {
+        using (gui.EnterFixedPositioning(buttonDisplayStyle.Size, buttonDisplayStyle.Size, default)) {
             gui.allocator = RectAllocator.Stretch;
             gui.spacing = 0f;
             Click clicked = gui.BuildFactorioObjectButton(goods, buttonDisplayStyle, tooltipOptions);
@@ -319,7 +319,7 @@ public static GoodsWithAmountEvent BuildFactorioObjectWithEditableAmount(this Im
         bool allowScroll = true, ObjectTooltipOptions tooltipOptions = default, SetKeyboardFocus setKeyboardFocus = SetKeyboardFocus.No) {
 
         using var group = gui.EnterGroup(default, RectAllocator.Stretch, spacing: 0f);
-        group.SetWidth(3f);
+        group.SetWidth(buttonDisplayStyle.Size);
         GoodsWithAmountEvent evt = (GoodsWithAmountEvent)gui.BuildFactorioObjectButton(obj, buttonDisplayStyle, tooltipOptions);
 
         if (gui.BuildFloatInput(amount, TextBoxDisplayStyle.FactorioObjectInput, setKeyboardFocus)) {

Yafc/Workspace/ProjectPageView.cs

@@ -65,7 +65,7 @@ public void Build(ImGui gui, Vector2 visibleSize) {
         base.Build(gui, visibleSize.Y - headerHeight, true);
     }
 
-    protected override Vector2 MeasureContent(float _, ImGui gui) => new Vector2(contentWidth, contentHeight);
+    public override Vector2 MeasureContent(float _, ImGui gui) => new Vector2(contentWidth, contentHeight);
 
     protected override void PositionContent(ImGui gui, Rect viewport) {
         headerContent.offset = new Vector2(-scrollX, 0);

Yafc/Workspace/SummaryView.cs

@@ -10,6 +10,9 @@
 namespace Yafc;
 
 public class SummaryView : ProjectPageView<Summary> {
+    /// <summary>Height of each row</summary>
+    private float rowHeight;
+
     /// <summary>Some padding to have the contents of the first column not 'stick' to the rest of the UI</summary>
     private readonly Padding FirstColumnPadding = new Padding(1f, 1.5f, 0, 0);
     private static float firstColumnWidth;
@@ -59,10 +62,12 @@ public override void BuildElement(ImGui gui, ProjectPage page) {
             foreach ((string name, GoodDetails details, bool enoughProduced) in view.GoodsToDisplay()) {
                 ProductionLink? link = table.links.Find(x => x.goods.name == name);
                 grid.Next();
+                bool isDrawn = false;
 
                 if (link != null) {
                     if (link.amount != 0f) {
                         DrawProvideProduct(gui, link, page, details, enoughProduced);
+                        isDrawn = true;
                     }
                 }
                 else {
@@ -72,9 +77,15 @@ public override void BuildElement(ImGui gui, ProjectPage page) {
                         if (Math.Abs(flow.amount) > Epsilon) {
 
                             DrawRequestProduct(gui, flow, enoughProduced);
+                            isDrawn = true;
                         }
                     }
                 }
+                if (!isDrawn) {
+                    // Reserve empty space to prevent 'compressing' empty rows
+                    _ = gui.AllocateRect(0f, view.rowHeight);
+                }
+
             }
         }
 
@@ -263,6 +274,7 @@ protected override async void BuildContent(ImGui gui) {
 
         if (gui.isBuilding) {
             firstColumnWidth = CalculateFirstColumWidth(gui);
+            rowHeight = ButtonDisplayStyle.ProductionTableUnscaled.Size + gui.PixelsToUnits(gui.GetFontSize().lineSize);
         }
 
         scrollArea.Build(gui);