Apply alignment xAlign to template residual path; add geometry assertions to alignment tests

Agent-Logs-Url: https://github.com/jongalloway/MarpToPptx/sessions/b58f9402-a58a-4139-b0fa-95eb48c28bcb

Co-authored-by: jongalloway <68539+jongalloway@users.noreply.github.com>

Author: Copilot

src/MarpToPptx.Pptx/Rendering/OpenXmlPptxRenderer.cs

@@ -1320,8 +1320,14 @@ element is HeadingElement h &&
                             }
                             break;
                         case ImageElement image:
+                            var residualXAlign = image.Alignment switch
+                            {
+                                "left" => 0.0,
+                                "right" => 1.0,
+                                _ => 0.5,
+                            };
                             AddImage(context, frame, image.Source, image.AltText, image.Caption,
-                                explicitWidth: image.ExplicitWidth, explicitHeight: image.ExplicitHeight, sizePercent: image.SizePercent);
+                                xAlign: residualXAlign, explicitWidth: image.ExplicitWidth, explicitHeight: image.ExplicitHeight, sizePercent: image.SizePercent);
                             break;
                         case VideoElement video:
                             AddVideo(context, frame, video.Source, video.AltText);

tests/MarpToPptx.Tests/PptxRendererTests.cs

@@ -948,6 +948,10 @@ public void Renderer_MarpitLeftAlignmentKeyword_RendersImageAtLeftEdgeOfFrame()
         // Marpit: ![left](image.jpg) floats the image to the left of the content area.
         // The "left" keyword is stripped from alt text; the image is placed at the left
         // edge of its allocated content frame (xAlign = 0.0).
+        //
+        // With default theme padding (Left=60 lu) and a 1×1 image in a 840×220 lu frame,
+        // CalculateImagePlacement gives X = 60 lu, width = height = 220 lu.
+        // In EMU (×12700): X = 762000, Cx = Cy = 2794000.
         using var workspace = TestWorkspace.Create();
 
         workspace.WriteFile("photo.png", Convert.FromBase64String(OnePxPngBase64));
@@ -971,6 +975,12 @@ public void Renderer_MarpitLeftAlignmentKeyword_RendersImageAtLeftEdgeOfFrame()
         var picture = Assert.Single(slidePart.Slide!.Descendants<P.Picture>());
         var description = picture.NonVisualPictureProperties?.NonVisualDrawingProperties?.Description?.Value;
         Assert.Equal(string.Empty, description);
+
+        // Left alignment: image X should be at the content frame's left edge (frame.X = 60 lu = 762000 EMU).
+        var transform = picture.ShapeProperties!.GetFirstChild<A.Transform2D>()!;
+        Assert.Equal(762000L, transform.Offset!.X!.Value);
+        Assert.Equal(2794000L, transform.Extents!.Cx!.Value);
+        Assert.Equal(2794000L, transform.Extents!.Cy!.Value);
     }
 
     [Fact]
@@ -979,6 +989,10 @@ public void Renderer_MarpitRightAlignmentKeyword_RendersImageAtRightEdgeOfFrame(
         // Marpit: ![right](image.jpg) floats the image to the right of the content area.
         // The "right" keyword is stripped from alt text; the image is placed at the right
         // edge of its allocated content frame (xAlign = 1.0).
+        //
+        // With default theme padding (Left=60 lu) and a 1×1 image in an 840×220 lu frame,
+        // gapX = 840 - 220 = 620 lu, so X = 60 + 620 = 680 lu → 8636000 EMU.
+        // Width = height = 220 lu → 2794000 EMU.
         using var workspace = TestWorkspace.Create();
 
         workspace.WriteFile("photo.png", Convert.FromBase64String(OnePxPngBase64));
@@ -1002,6 +1016,13 @@ public void Renderer_MarpitRightAlignmentKeyword_RendersImageAtRightEdgeOfFrame(
         var picture = Assert.Single(slidePart.Slide!.Descendants<P.Picture>());
         var description = picture.NonVisualPictureProperties?.NonVisualDrawingProperties?.Description?.Value;
         Assert.Equal(string.Empty, description);
+
+        // Right alignment: gapX = frameWidth - fittedWidth = 840 - 220 = 620 lu,
+        // so X = frame.X + gapX = 60 + 620 = 680 lu → 8636000 EMU.
+        var transform = picture.ShapeProperties!.GetFirstChild<A.Transform2D>()!;
+        Assert.Equal(8636000L, transform.Offset!.X!.Value);
+        Assert.Equal(2794000L, transform.Extents!.Cx!.Value);
+        Assert.Equal(2794000L, transform.Extents!.Cy!.Value);
     }
 
     [Fact]