Show preview margins

src/dymoprint/gui/gui.py

@@ -8,6 +8,7 @@
 from PyQt6.QtGui import QIcon, QPixmap
 from PyQt6.QtWidgets import (
     QApplication,
+    QCheckBox,
     QComboBox,
     QGraphicsDropShadowEffect,
     QHBoxLayout,
@@ -58,6 +59,7 @@ def __init__(self):
         self.min_label_width_mm = QSpinBox()
         self.justify = QComboBox()
         self.info_label = QLabel()
+        self.preview_show_margins = QCheckBox()
         self.last_error = None
         self.dymo_labeler = None
 
@@ -104,6 +106,7 @@ def init_elements(self):
         self.background_color.addItems(
             ["white", "black", "yellow", "blue", "red", "green"]
         )
+        self.preview_show_margins.setChecked(False)
 
         self.update_params()
         self.label_list.populate()
@@ -126,6 +129,7 @@ def init_connections(self):
         self.label_list.renderPrintPreviewSignal.connect(self.update_preview_render)
         self.label_list.renderPrintPayloadSignal.connect(self.update_print_render)
         self.print_button.clicked.connect(self.print_label)
+        self.preview_show_margins.stateChanged.connect(self.update_params)
 
     def init_layout(self):
         settings_widget = QToolBar(self)
@@ -145,6 +149,8 @@ def init_layout(self):
         settings_widget.addWidget(self.foreground_color)
         settings_widget.addWidget(QLabel(" on "))
         settings_widget.addWidget(self.background_color)
+        settings_widget.addWidget(QLabel("Show margins:"))
+        settings_widget.addWidget(self.preview_show_margins)
 
         render_widget = QWidget(self)
         label_render_widget = QWidget(render_widget)
@@ -189,6 +195,7 @@ def update_params(self):
         self.render_context.foreground_color = self.foreground_color.currentText()
         self.render_context.background_color = self.background_color.currentText()
         self.render_context.height_px = self.dymo_labeler.height_px
+        self.render_context.preview_show_margins = self.preview_show_margins.isChecked()
 
         self.label_list.update_params(
             dymo_labeler=self.dymo_labeler,

src/dymoprint/gui/q_dymo_labels_list.py

@@ -187,7 +187,7 @@ def render_print(self):
             min_width_px=mm_to_px(self.min_label_width_mm),
         )
         try:
-            bitmap = render_engine.render(self.render_context)
+            bitmap, _ = render_engine.render(self.render_context)
         except BaseException as err:  # noqa: BLE001
             crash_msg_box(self, "Render Engine Failed!", err)
             bitmap = EmptyRenderEngine().render(self.render_context)

src/dymoprint/lib/render_engines/margins.py

@@ -104,4 +104,8 @@ def render(self, context: RenderContext) -> Image.Image:
         bitmap.paste(
             payload_bitmap, box=(round(horizontal_offset_px), round(vertical_offset_px))
         )
-        return bitmap
+        meta = {
+            "horizontal_offset_px": horizontal_offset_px,
+            "vertical_offset_px": vertical_offset_px,
+        }
+        return bitmap, meta

src/dymoprint/lib/render_engines/print_preview.py

@@ -1,13 +1,16 @@
 from __future__ import annotations
 
-from PIL import Image, ImageColor, ImageOps
+from PIL import Image, ImageColor, ImageDraw, ImageOps
 
 from dymoprint.lib.render_engines.margins import MarginsMode, MarginsRenderEngine
 from dymoprint.lib.render_engines.render_context import RenderContext
 from dymoprint.lib.render_engines.render_engine import RenderEngine
 
 
 class PrintPreviewRenderEngine(RenderEngine):
+    MARGIN_PX = 20
+    DX = MARGIN_PX * 0.2
+
     def __init__(
         self,
         render_engine: RenderEngine,
@@ -29,7 +32,7 @@ def __init__(
         )
 
     def _get_preview_bitmap(self, context: RenderContext):
-        label_bitmap = self.render_engine.render(context)
+        label_bitmap, meta = self.render_engine.render(context)
         bitmap = ImageOps.invert(label_bitmap.convert("L")).convert("RGBA")
         pixel_map = {
             "black": context.foreground_color,
@@ -44,7 +47,41 @@ def _get_preview_bitmap(self, context: RenderContext):
         for x in range(0, width):
             for y in range(0, height):
                 pixdata[x, y] = pixel_map[pixdata[x, y]]
-        return bitmap
+        return bitmap, meta
+
+    def _show_margins(self, preview_bitmap, bitmap, meta, context):
+        draw = ImageDraw.Draw(bitmap)
+        x = meta["horizontal_offset_px"]
+        y = meta["vertical_offset_px"]
+        width, height = bitmap.size
+        preview_width, preview_height = preview_bitmap.size
+        lines = [
+            (self.MARGIN_PX + x, 0, self.MARGIN_PX + x, height),
+            (
+                self.MARGIN_PX + preview_width - x,
+                0,
+                self.MARGIN_PX + preview_width - x,
+                height,
+            ),
+            (0, self.MARGIN_PX + y, width, self.MARGIN_PX + y),
+            (
+                0,
+                self.MARGIN_PX + preview_height - y,
+                width,
+                self.MARGIN_PX + preview_height - y,
+            ),
+        ]
+        for line in lines:
+            draw.line(line, fill=context.foreground_color)
 
     def render(self, context: RenderContext) -> Image.Image:
-        return self._get_preview_bitmap(context)
+        preview_bitmap, meta = self._get_preview_bitmap(context)
+        preview_width, preview_height = preview_bitmap.size
+        width = preview_width + self.MARGIN_PX * 2
+        height = preview_height + self.MARGIN_PX * 2
+        bitmap = Image.new("RGBA", (width, height), color=(255, 0, 0, 0))
+        bitmap.paste(preview_bitmap, box=(self.MARGIN_PX, self.MARGIN_PX))
+        if context.preview_show_margins:
+            self._show_margins(preview_bitmap, bitmap, meta, context)
+
+        return bitmap

src/dymoprint/lib/render_engines/render_context.py

@@ -5,6 +5,7 @@ class _RenderContextFieldName(Enum):
     BACKGROUND_COLOR = 1
     FOREGROUND_COLOR = 2
     HEIGHT_PX = 3
+    PREVIEW_SHOW_MARGINS = 4
 
 
 class RenderContext: