--- name: slide-craft title: "页面设计" description: The design law of a slide page — canvas geometry, the text height table, the type scale, contrast pairs, spacing rhythm, and which element type carries which content. Load it when patching slide elements one at a time, when a fix is about colour or contrast, when text has to grow or shrink inside a box, when a page feels crowded or empty, or when replacement content needs real rich-text structure. It is the standard `page-clone` and `pro-editing` edit against, not a procedure of its own — those two decide which pages to touch and in what order, this one decides what a good page looks like when you put it back. --- # The design law of a slide page Every slide in this runtime was drawn under a long set of rules — the canvas, the height table, the type scale, the spacing standards. The generator that drew the page had all of them in front of it. When you patch one element, you have the page's numbers and nothing else, and the rules are the only way to tell a repair from a dent. This is that rule set, restated for editing. It is about the page, not the process: which numbers a change has to stay consistent with, and which fields actually reach the screen. ## The canvas you are editing inside The canvas is **1000 × 562.5**. All elements respect a **50px margin**, so the live area is `left ∈ [50, 950]`, `top ∈ [50, 512.5]`, and an element's right edge (`left + width`) stays ≤ 950, its bottom edge ≤ 512.5. The page's own alignment grid, which existing elements are already on: - Left-aligned content sits at `left = 60` or `left = 80`. - Centred content is `left = (1000 - width) / 2` — recomputed, never guessed. - Right-aligned content is `left = 1000 - width - 60`. Changing `width` on centred content changes `left` too, and they are two separate writes. Read the neighbours' boxes first and land on the column they are already using; a lone element 8px off the shared left edge reads as a mistake even though nothing overflows. **There is no alignment operation.** Every position is an explicit number you write to that element's own `left` / `top` / `width` / `height`, one path per call, computed from the neighbours you read. Aligning a row means giving each element the number the row already uses — not asking the page to tidy itself. ## Text is sized by table, not by eye A text element has **10px padding on all four sides**, so its usable area is `(width - 20) × (height - 20)`, and heights come from one table (line-height 1.5, padding included): | Font size | 1 line | 2 lines | 3 lines | 4 lines | 5 lines | | --------- | ------ | ------- | ------- | ------- | ------- | | 14px | 43 | 64 | 85 | 106 | 127 | | 16px | 46 | 70 | 94 | 118 | 142 | | 18px | 49 | 76 | 103 | 130 | 157 | | 20px | 52 | 82 | 112 | 142 | 172 | | 24px | 58 | 94 | 130 | 166 | 202 | | 28px | 64 | 106 | 148 | 190 | 232 | | 32px | 70 | 118 | 166 | 214 | 262 | | 36px | 76 | 130 | 184 | 238 | 292 | When you replace an element's words, re-derive its height instead of keeping the old one: 1. `characters_per_line = (width - 20) / font_size`. Keep the longest line at **≤ 75%** of that; past 100% the text wraps and takes a row you did not budget. 2. Count the lines your new content needs — one per `

`, plus a wrap for every paragraph over `characters_per_line` — then add ~0.8 of a line of slack and round up. 3. Look the height up against the **largest font size present in the content**, not the average. Height is a container, not a clamp: overflowing text spills past the box rather than shrinking, and the page shows the spill. The fix order is **shorten the words, then step to the next table row, then widen the box** — in that order, because a slide that needs a bigger box usually needs fewer words. ## The type scale | Content | Size | | ----------- | ------- | | Main title | 32-36px | | Subtitle | 24-28px | | Key points | 18-20px | | Body | 16-18px | | Caption | 14-16px | Levels stay 2-4px apart and everything at one level uses one size. When you touch an element, take its size from the siblings that share its role on that page rather than from this table fresh — the page's own scale wins, and this table is how you recognise which level an element belongs to. **Size lives in the content HTML**, as inline `font-size` on the `

` — there is no font-size field to write. So changing a size means writing the whole content string back, which means you have to know the markup you are replacing. ## What the renderer really does with your HTML The `content` of a text element is an HTML string, and this page's CSS resets most tag semantics. Four consequences decide how you write rich text: - **`