support for displaying images in webview

[mahmoodsh36]

No description provided.

[code-contractor-app]

❌ Code Contractor Validation: FAILED

=== Contract: contract ===

✓ Code Contractor Validation Result
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📋 Contract Source: Repository

📊 Statistics:
  Files Changed:    13
  Lines Added:      942
  Lines Deleted:    133
  Total Changed:    1075
  Delete Ratio:     0.12 (12%)

Status: FAILED ❌

🤖 AI Providers:
  - codex — model: (Codex default)

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⚠️ Violations Found (2):

[WARNING] max_files_changed
  Too many files changed: 13 > 10
  Limit: 10
  Actual: 13

[WARNING] max_total_changed_lines
  Too many lines changed: 1075 > 400
  Limit: 400
  Actual: 1075

📋 Contract Configuration: contract (Source: Repository)

version: 2

trigger:
  paths:
    - "extensions/**"
    - "frontends/**/*.lisp"
    - "src/**"
    - "tests/**"
    - "contrib/**"
    - "**/*.asd"
  head_branches:
    exclude:
      - 'revert-*'

validation:
  limits:
    max_total_changed_lines: 400
    max_delete_ratio: 0.5
    max_files_changed: 10
    severity: warning

  ai:
    system_prompt: |
      You are a senior Common Lisp engineer reviewing code for Lem editor.
      Lem is a text editor with multiple frontends (ncurses, SDL2, webview).
      Focus on maintainability, consistency with existing code, and Lem-specific conventions.
    rules:
      # === File Structure ===
      - name: defpackage_rule
        prompt: |
          First form must be `defpackage` or `uiop:define-package`.
          Package name should match filename (e.g., `foo.lisp` → `:lem-ext/foo` or `:lem-foo`).
          Extensions must use `lem-` prefix (e.g., `:lem-python-mode`).

      - name: file_structure_rule
        prompt: |
          File organization (top to bottom):
          1. defpackage
          2. defvar/defparameter declarations
          3. Key bindings (define-key, define-keys)
          4. Class/struct definitions
          5. Functions and commands

      # === Style ===
      - name: loop_keywords_rule
        prompt: |
          Loop keywords must use colons: `(loop :for x :in list :do ...)`
          NOT: `(loop for x in list do ...)`

      - name: naming_conventions_rule
        prompt: |
          Naming conventions:
          - Functions/variables: kebab-case (e.g., `find-buffer`)
          - Special variables: *earmuffs* (e.g., `*global-keymap*`)
          - Constants: +plus-signs+ (e.g., `+default-tab-size+`)
          - Predicates: -p suffix for functions (e.g., `buffer-modified-p`)
          - Do NOT use -p suffix for user-configurable variables

      # === Documentation ===
      - name: docstring_rule
        prompt: |
          Required docstrings for:
          - Exported functions, methods, classes
          - `define-command` (explain what the command does)
          - Generic functions (`:documentation` option)
          Important functions should explain "why", not just "what".
        severity: warning

      # === Lem-Specific ===
      - name: internal_symbol_rule
        prompt: |
          Use exported symbols from `lem` or `lem-core` package.
          Avoid `lem::internal-symbol` access.
          If internal access is necessary, document why.

      - name: error_handling_rule
        prompt: |
          - `error`: Internal/programming errors
          - `editor-error`: User-facing errors (displayed in echo area)
          Always use `editor-error` for messages shown to users.

      - name: frontend_interface_rule
        prompt: |
          Frontend-specific code must use `lem-if:*` protocol.
          Do not call frontend implementation directly from core.
        severity: warning

      # === Functional Style ===
      - name: functional_style_rule
        prompt: |
          Prefer explicit function arguments over dynamic variables.
          Avoid using `defvar` for state passed between functions.
          Exception: Well-documented cases like `*current-buffer*`.

      - name: dynamic_symbol_call_rule
        prompt: |
          Avoid `uiop:symbol-call`. Rethink architecture instead.
          If unavoidable, document the reason.

      # === Libraries ===
      - name: alexandria_usage_rule
        prompt: |
          Alexandria utilities allowed: `if-let`, `when-let`, `with-gensyms`, etc.
          Avoid: `alexandria:curry` (use explicit lambdas)
          Avoid: `alexandria-2:*` functions not yet used in codebase

      # === Macros ===
      - name: macro_style_rule
        prompt: |
          Keep macros small. For complex logic, use `call-with-*` pattern:
          ```lisp
          (defmacro with-foo (() &body body)
            `(call-with-foo (lambda () ,@body)))
          ```
          Prefer `list` over backquote outside macros.

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[code-contractor-app]

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[mahmoodsh36]

this introduces functionality to display in webview, the functionality exists in the sdl2 frontend but not in webview.

the functionality so far is very basic and only works properly with images that originate from attributes of virtual text that originates from an overlay, by virtual text i mean the :before-item/:after-item stuff that was introduced in #2230, because the cursor is meant to skip over those virtual items. and currently when the cursor goes over non-virtual images the buffer gets confused.

the core currently uses a uniform grid for displaying text which makes it hard to work with arbitrarily sized objects so we round image sizes to multiples of cell sizes.

selecting text with cursor doesnt work because images dont align with the buffer flow so the client doesnt properly resolve cursor click position relevant to the text grid. hoping to addess this soon.

[mahmoodsh36]

example usage:

(lem:define-command webview-image-demo () ()
  (let* ((image (namestring (asdf:system-relative-pathname :lem #p"resources/lem.png")))
         (attr (lem:make-attribute :plist (list :image image :pixel-width 300 :pixel-height 150)))
         (buffer (lem:make-buffer "*image-demo*"))
         (point (lem:buffer-point buffer)))
    (lem:switch-to-buffer buffer)
    (lem:erase-buffer buffer)
    (lem:insert-string point (format nil "before X after~%more text~%"))
    (lem:with-point ((s point)
                     (e point))
      (lem:buffer-start s)
      (lem:character-offset s 7)
      (lem:move-point e s)
      (lem:character-offset e 1)
      (let ((ov (lem:make-overlay s e attr)))
        (lem:overlay-put
         ov
         :cursor-enter-functions (list 'lem:move-point-out-of-overlay))))
    (lem:buffer-start point)))

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Code Contractor validation failed ❌ — see the sticky comment for full results.

[mahmoodsh36]

this PR contains more than just 'image support for webview', i unified some of the rendering/layout code between the different frontends. the webview doesnt use a grid of uniform cells anymore, and it mainly uses pixels for sizing things instead of cells, like the sdl2 frontend does.

this PR is a follow-up for #2230