Add scroll/pan support for Sta preview mode

- Right-click drag to pan the canvas in static mode
- Scroll position (X/Y) persisted across sessions
- Uses independent zoom and scroll settings from One/All modes

aniphallow.lua

@@ -118,6 +118,12 @@ local S = {
     previewLayoutValue = 2,           -- number for fixed cols/rows
     previewMode        = "all",       -- "all", "single", or "static"
     previewSingleIdx   = 1,           -- which animation to show in single mode
+    -- Static preview scroll/pan
+    previewStaScrollX  = 0,
+    previewStaScrollY  = 0,
+    previewStaDragging = false,
+    previewStaDragLastX = 0,
+    previewStaDragLastY = 0,
     -- Current preset
     currentPreset      = "Default",
 }
@@ -414,6 +420,8 @@ local function saveMaster()
     f:write("previewZoomAll=" .. S.previewZoomAll .. "\n")
     f:write("previewZoomOne=" .. S.previewZoomOne .. "\n")
     f:write("previewZoomSta=" .. S.previewZoomSta .. "\n")
+    f:write("previewStaScrollX=" .. S.previewStaScrollX .. "\n")
+    f:write("previewStaScrollY=" .. S.previewStaScrollY .. "\n")
     f:write("previewSingleIdx=" .. S.previewSingleIdx .. "\n")
     -- File associations
     for filepath, preset in pairs(filePresetMap) do
@@ -442,6 +450,8 @@ local function loadMaster()
             if k == "previewZoomAll" then S.previewZoomAll = tonumber(v) or DEFAULT_PREVIEW_ZOOM end
             if k == "previewZoomOne" then S.previewZoomOne = tonumber(v) or DEFAULT_PREVIEW_ZOOM end
             if k == "previewZoomSta" then S.previewZoomSta = tonumber(v) or DEFAULT_PREVIEW_ZOOM end
+            if k == "previewStaScrollX" then S.previewStaScrollX = tonumber(v) or 0 end
+            if k == "previewStaScrollY" then S.previewStaScrollY = tonumber(v) or 0 end
             if k == "previewSingleIdx" then S.previewSingleIdx = tonumber(v) or 1 end
             if k == "presetNames" and v ~= "" then
                 knownPresetNames = {}
@@ -1407,21 +1417,23 @@ openPreviewWindow = function()
         onpaint = function(ev)
             local gc = ev.context
 
-            -- Static mode: render full sprite canvas
+            -- Static mode: render full sprite canvas with scroll offset
             if S.previewMode == "static" then
                 if S.sourceImage then
                     local z = pvZoom()
+                    local sx = S.previewStaScrollX
+                    local sy = S.previewStaScrollY
                     local sw = S.sourceImage.width * z
                     local sh = S.sourceImage.height * z
                     if S.useBgColor then
                         gc.color = S.bgColor
-                        gc:fillRect(Rectangle(0, 0, sw, sh))
+                        gc:fillRect(Rectangle(sx, sy, sw, sh))
                     else
-                        drawCheckerboard(gc, sw, sh, z, 0, 0)
+                        drawCheckerboard(gc, sw, sh, z, sx, sy)
                     end
                     gc:drawImage(S.sourceImage,
                         Rectangle(0, 0, S.sourceImage.width, S.sourceImage.height),
-                        Rectangle(0, 0, sw, sh))
+                        Rectangle(sx, sy, sw, sh))
                 end
                 return
             end
@@ -1492,7 +1504,15 @@ openPreviewWindow = function()
             end
         end,
         onmousedown = function(ev)
-            if S.previewMode == "static" then return end
+            -- Static mode: right-click drag to scroll
+            if S.previewMode == "static" then
+                if ev.button == MouseButton.RIGHT then
+                    S.previewStaDragging = true
+                    S.previewStaDragLastX = ev.x
+                    S.previewStaDragLastY = ev.y
+                end
+                return
+            end
             -- In single mode: L-click=prev anim, R-click=next anim
             if S.previewMode == "single" then
                 if ev.button == MouseButton.LEFT then
@@ -1518,6 +1538,22 @@ openPreviewWindow = function()
                 end
             end
         end,
+        onmousemove = function(ev)
+            if S.previewMode == "static" and S.previewStaDragging then
+                local dx = ev.x - S.previewStaDragLastX
+                local dy = ev.y - S.previewStaDragLastY
+                S.previewStaScrollX = S.previewStaScrollX + dx
+                S.previewStaScrollY = S.previewStaScrollY + dy
+                S.previewStaDragLastX = ev.x
+                S.previewStaDragLastY = ev.y
+                previewDlg:repaint()
+            end
+        end,
+        onmouseup = function(ev)
+            if S.previewMode == "static" then
+                S.previewStaDragging = false
+            end
+        end,
         onwheel = function(ev)
             local dz = ev.deltaY < 0 and 1 or -1
             if S.previewMode == "single" then