add error box to prevent an occasional panic when the start or end pos wasn't set right

main.go

@@ -290,6 +290,7 @@ func main() {
 	editModeWidth := false
 	editModeHeight := false
 	generateGridError := false
+	posError := false
 
 	toolOptions := []string{"Wall", "Start", "End", "Erase"}
 	toolOptionsText := strings.Join(toolOptions, ";")
@@ -467,6 +468,13 @@ func main() {
 			}
 		}
 
+		if posError {
+			result := rg.MessageBox(rl.NewRectangle(screenWidth/2-(100*scale), screenHeight/2-(40*scale), (200*scale), (120*scale)), "Error", "Start and end positions must be\nwithin the generated grid", "OK")
+			if result >= 0 {
+				posError = false
+			}
+		}
+
 		// Generate Grid Button
 		if rg.Button(rl.NewRectangle(sidebarX+(10*scale), (40*scale), (180*scale), (30*scale)), "Generate Grid") {
 			width, _ = strconv.Atoi(widthInputValue)
@@ -521,6 +529,9 @@ func main() {
 
 		// Calculate Path Button
 		if rg.Button(rl.NewRectangle(sidebarX+(10*scale), (screenHeight-(40*scale)), (180*scale), (30*scale)), "Calculate Path") {
+			if int(startPos.X) < 0 || int(startPos.X) >= width || int(startPos.Y) < 0 || int(startPos.Y) >= height || int(endPos.X) < 0 || int(endPos.X) >= width || int(endPos.Y) < 0 || int(endPos.Y) >= height {
+				posError = true
+			} else {
 				astar.ResetGrid(false) // keep grid types, otherwise it will delete the board before simulating
 				astar.SetHeuristic(activeHeuristic)
 				gridTypes := astar.GetGridTypes()
@@ -555,6 +566,7 @@ func main() {
 				}
 				tex.markFull()
 			}
+		}
 
 		// Status Label
 		rg.Label(rl.NewRectangle((10*scale), (screenHeight-(30*scale)), (180*scale), (30*scale)), "Evaluated "+strconv.Itoa(astar.GetEvaluatedCells())+" cells in "+astar.GetTimeTaken().String())