Show proportional rectangles comparing original image dimensions
(gray) vs target output dimensions (blue). Preview updates live
as the user changes width/height values. Uses first loaded image
for actual dimensions when available.
Add per-format mapping rows in convert step advanced options so each
input format can target a different output format. Move basic
orientation controls (rotate/flip) into the resize step per design doc
specification that these should be folded into the resize step.
All four configurable steps (resize, convert, compress, metadata) now
have signal handlers that update the shared JobConfig via AppState.
The run_processing function builds ProcessingJob from actual user
choices instead of hardcoded values. Fixed clippy warnings (collapsed
if-let chain, removed needless borrow).
Full Adwaita widget-based layouts for all 7 wizard steps with
PreferencesGroups, SwitchRows, SpinRows, ComboRows, FlowBoxes,
ExpanderRows for social media presets, quality slider with named
marks, metadata radio group, and output configuration.
