Fix #74, by forcing scroll views to scroll up until items are visible. (

#126)

Sometimes the search bar seemed to return nothing when there are 
items that match. That happened because the scrolling view was not 
reset, which resulted in showing empty space until you scroll back up.

This PR fixes that issue. It fixes at least the object explorer 
(SelectObjectPanels) and the production sheet list 
(MainScreen.allPages), and it doesn't visibly affect the production tables.

FactorioCalc.sln

@@ -13,6 +13,11 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CommandLineToolExample", "C
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Yafc.Model.Tests", "Yafc.Model.Tests\Yafc.Model.Tests.csproj", "{66B66728-84F0-4242-B49A-B9D746A3CCA5}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{D6A715CB-5C17-4DD7-9ADA-5D7F44FADFCF}"
+	ProjectSection(SolutionItems) = preProject
+		changelog.txt = changelog.txt
+	EndProjectSection
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -44,4 +49,7 @@ Global
 		{66B66728-84F0-4242-B49A-B9D746A3CCA5}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{66B66728-84F0-4242-B49A-B9D746A3CCA5}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
 EndGlobal

Yafc.UI/ImGui/ScrollArea.cs

@@ -202,14 +202,16 @@ public class ScrollArea(float height, GuiBuilder builder, Padding padding = defa
 
     public class VirtualScrollList<TData> : ScrollAreaBase {
         private readonly Vector2 elementSize;
-        protected readonly int bufferRows;
-        protected int firstVisibleBlock;
-        protected int elementsPerRow;
+        // When rendering the scrollable content, render 'blocks' of 4 rows at a time. (As far as I can tell, any positive value works. Shadow picked 4, so I kept that.)
+        private readonly int bufferRows = 4;
+        // The first block of bufferRows that was rendered last time BuildContents was called. If it changes while scrolling, we need to re-render the scrollable content.
+        private int firstVisibleBlock;
+        private int elementsPerRow;
         private IReadOnlyList<TData> _data = [];
         private readonly int maxRowsVisible;
         private readonly Drawer drawer;
-        public float _spacing;
-        protected readonly Action<int, int> reorder;
+        private float _spacing;
+        private readonly Action<int, int> reorder;
 
         public float spacing {
             get => _spacing;
@@ -229,10 +231,9 @@ public IReadOnlyList<TData> data {
             }
         }
 
-        public VirtualScrollList(float height, Vector2 elementSize, Drawer drawer, int bufferRows = 4, Padding padding = default, Action<int, int> reorder = null, bool collapsible = false) : base(height, padding, collapsible) {
+        public VirtualScrollList(float height, Vector2 elementSize, Drawer drawer, Padding padding = default, Action<int, int> reorder = null, bool collapsible = false) : base(height, padding, collapsible) {
             this.elementSize = elementSize;
             maxRowsVisible = MathUtils.Ceil(height / this.elementSize.Y) + bufferRows + 1;
-            this.bufferRows = bufferRows;
             this.drawer = drawer;
             this.reorder = reorder;
         }
@@ -258,9 +259,13 @@ protected override void BuildContents(ImGui gui) {
 
             int rowCount = ((_data.Count - 1) / elementsPerRow) + 1;
             firstVisibleBlock = CalcFirstBlock();
-            int firstRow = firstVisibleBlock * bufferRows;
+            // Scroll up until there are maxRowsVisible, or to the top.
+            int firstRow = Math.Max(0, Math.Min(firstVisibleBlock * bufferRows, rowCount - maxRowsVisible));
             int index = firstRow * elementsPerRow;
             if (index >= _data.Count) {
+                // If _data is empty, there's nothing to draw. Make sure MeasureContent reports that, instead of the size of the most recent non-empty content.
+                // This will remove the scroll bar when the search doesn't match anything.
+                gui.lastContentRect = new Rect(gui.lastContentRect.X, gui.lastContentRect.Y, 0, 0);
                 return;
             }
 

changelog.txt

@@ -5,6 +5,7 @@ Date: soon
         - Add a help message and proper handling for command line arguments
         - Removed default pollution cost from calculation. Added a setting to customize pollution cost.
         - Add fuel consumption recipe for products
+        - Fix list displays below search boxes. If necessary, they now scroll up until items are visible.
 ----------------------------------------------------------------------------------------------------------------------
 Version: 0.6.4
 Date: April 16th 2024