initial commit

syslib/doublebuf.lua

@@ -0,0 +1,61 @@
+-- syslib/doublebuf.lua
+--
+-- Optional sprite/backbuffer wrapper.
+--
+-- Why:
+--   On SPI LCDs (like the M5Cardputer's ST7789), direct drawing often flickers because
+--   the display is showing the framebuffer while you "clear then draw" each frame.
+--   The fix is to render into an off-screen buffer (a sprite/canvas), then push the
+--   finished frame to the display in one shot.
+
+local M = {}
+
+local function hasSpriteAPI(gfx)
+    return type(gfx) == "table" and type(gfx.newSprite) == "function"
+end
+
+function M.new(gfx, w, h)
+    if hasSpriteAPI(gfx) then
+        local sprite = gfx.newSprite(w, h)
+
+        local g = {
+            clear = function(c) return sprite:clear(c) end,
+            setTextColor = function(fg, bg) return sprite:setTextColor(fg, bg) end,
+            setTextSize = function(sz) return sprite:setTextSize(sz) end,
+            drawString = function(text, x, y) return sprite:drawString(text, x, y) end,
+            drawCenterString = function(text, x, y) return sprite:drawCenterString(text, x, y) end,
+        }
+
+        return {
+            g = g,
+            isBuffered = true,
+            present = function()
+                -- Push the completed frame. If your binding supports DMA, this should use it.
+                return sprite:push(0, 0)
+            end,
+            free = function()
+                if sprite and type(sprite.free) == "function" then sprite:free() end
+            end,
+        }
+    end
+
+    -- Unbuffered fallback: proxy directly to gfx's module-level functions.
+    local g = {
+        clear = function(c) return gfx.clear(c) end,
+        setTextColor = function(fg, bg) return gfx.setTextColor(fg, bg) end,
+        setTextSize = function(sz) return gfx.setTextSize(sz) end,
+        drawString = function(text, x, y) return gfx.drawString(text, x, y) end,
+        drawCenterString = function(text, x, y) return gfx.drawCenterString(text, x, y) end,
+    }
+
+    return {
+        g = g,
+        isBuffered = false,
+        present = function() end,
+        free = function() end,
+    }
+end
+
+return M
+
+