Summary
Implement a first practical subset of Marpit image alignment and multi-image composition behaviors as a slice of #103.
Motivation
After background-image and image-sizing support, the next compatibility gap is image placement and composition. These behaviors affect how real-world decks lay out side-by-side or aligned images.
Proposed Scope
Support a bounded first slice that includes:
- alignment / placement variants such as
left and right
- representative multi-image composition cases documented by Marpit
- explicit fallback behavior for composition patterns that cannot yet be matched faithfully in PPTX
Acceptance Criteria
- Supported alignment forms visibly affect placement in generated PPTX output.
- At least one representative multi-image composition scenario is covered.
- Parser and renderer tests cover the supported alignment/composition cases.
- Limitations are documented where full Marpit parity is not yet achieved.
Relationship To Parent
Tracked under #103 as the placement and composition slice after syntax scaffolding and core sizing/background support.
Implementation Starting Points
Key files to extend (do not create parallel parsing paths):
src/MarpToPptx.Core/Parsing/MarpitImageSizingParser.cs — strip left/right keywords from alt text and return them as parsed alignment values, following the same pattern used for w:/h: and % tokens.src/MarpToPptx.Core/Parsing/MarpMarkdownParser.cs (~line 540) — the bg alt-text branch already handles background image promotion; extend it to recognise bg left/bg right for split-background layout.src/MarpToPptx.Core/Models/ImageElement.cs — thread a new alignment property through the model so the renderer can consume it.src/MarpToPptx.Pptx/Rendering/OpenXmlPptxRenderer.cs — AddImage already accepts xAlign/yAlign parameters and CalculateImagePlacement honours them; wire the parsed alignment into these existing parameters.tests/MarpToPptx.Tests/ParserTests.cs and tests/MarpToPptx.Tests/PptxRendererTests.cs — the compatibility matrix tests (Parser_MarpitLeftAlignmentKeyword_*, Renderer_MarpitLeftAlignmentKeyword_*, etc.) document the current gap; update them to assert on actual position/alignment values once the feature lands.
Summary
Implement a first practical subset of Marpit image alignment and multi-image composition behaviors as a slice of #103.
Motivation
After background-image and image-sizing support, the next compatibility gap is image placement and composition. These behaviors affect how real-world decks lay out side-by-side or aligned images.
Proposed Scope
Support a bounded first slice that includes:
leftandrightAcceptance Criteria
Relationship To Parent
Tracked under #103 as the placement and composition slice after syntax scaffolding and core sizing/background support.
Implementation Starting Points
Key files to extend (do not create parallel parsing paths):
src/MarpToPptx.Core/Parsing/MarpitImageSizingParser.cs— stripleft/rightkeywords from alt text and return them as parsed alignment values, following the same pattern used forw:/h:and%tokens.src/MarpToPptx.Core/Parsing/MarpMarkdownParser.cs(~line 540) — thebgalt-text branch already handles background image promotion; extend it to recognisebg left/bg rightfor split-background layout.src/MarpToPptx.Core/Models/ImageElement.cs— thread a new alignment property through the model so the renderer can consume it.src/MarpToPptx.Pptx/Rendering/OpenXmlPptxRenderer.cs—AddImagealready acceptsxAlign/yAlignparameters andCalculateImagePlacementhonours them; wire the parsed alignment into these existing parameters.tests/MarpToPptx.Tests/ParserTests.csandtests/MarpToPptx.Tests/PptxRendererTests.cs— the compatibility matrix tests (Parser_MarpitLeftAlignmentKeyword_*,Renderer_MarpitLeftAlignmentKeyword_*, etc.) document the current gap; update them to assert on actual position/alignment values once the feature lands.