Module: gameui.context

Source: ./gameui/context.reef

Overview

gameui/context.reef - Immediate mode UI context Part of reef-stdlib Game UI module

The UIContext is the core of the immediate mode UI system. Unlike retained mode UI where widgets are created once and persist, immediate mode rebuilds the UI every frame. This is simpler for game UIs that change frequently.

Usage pattern: let ctx = ui_context(surface, input) ui_begin_frame(ctx) if ui_button(ctx, "Play") { start_game() } if ui_checkbox(ctx, "Sound", &sound_enabled) { ... } ui_end_frame(ctx)

Types

StateEntry

Fields:

Name	Type
`id`	`int`
`float_value`	`float`
`bool_value`	`bool`
`has_float`	`bool`
`has_bool`	`bool`

UIContext

Fields:

Name	Type
`surface`	`surface.Surface`
`input`	`input.InputState`
`style`	`style.Style`
`next_id`	`int`
`id_stack`	`[int]`
`id_stack_size`	`int`
`hot_id`	`int`
`active_id`	`int`
`cursor_x`	`float`
`cursor_y`	`float`
`line_height`	`float`
`indent_level`	`float`
`same_line`	`bool`
`clip_stack`	`[core.Rect]`
`clip_stack_size`	`int`
`state`	`[StateEntry]`
`state_count`	`int`

Functions

`fn ui_context(surf: surface.Surface, inp: input.InputState): UIContext`

`fn ui_context_with_style(surf: surface.Surface, inp: input.InputState, st: style.Style): UIContext`

`fn ui_gen_id(ctx: UIContext): int`

`fn ui_push_id(ctx: UIContext, id: int): UIContext`

`fn ui_pop_id(ctx: UIContext): UIContext`

`fn ui_get_id(ctx: UIContext, name: string): int`

`fn string_hash(s: string): int`

`fn string_length(s: string): int`

`fn char_at(s: string, idx: int): int`

`fn ui_set_hot(ctx: UIContext, id: int): UIContext`

`fn ui_set_active(ctx: UIContext, id: int): UIContext`

`fn ui_clear_active(ctx: UIContext): UIContext`

`fn ui_is_hot(ctx: UIContext, id: int): bool`

`fn ui_is_active(ctx: UIContext, id: int): bool`

`fn ui_cursor(ctx: UIContext): core.Point`

`fn ui_set_cursor(ctx: UIContext, x: float, y: float): UIContext`

`fn ui_advance_cursor(ctx: UIContext, dx: float, dy: float): UIContext`

`fn ui_same_line(ctx: UIContext): UIContext`

`fn ui_new_line(ctx: UIContext): UIContext`

`fn ui_indent(ctx: UIContext, amount: float): UIContext`

`fn ui_unindent(ctx: UIContext, amount: float): UIContext`

`fn ui_space(ctx: UIContext, amount: float): UIContext`

`fn ui_push_clip(ctx: UIContext, rect: core.Rect): UIContext`

`fn ui_pop_clip(ctx: UIContext): UIContext`

`fn ui_get_clip(ctx: UIContext): core.Rect`

`fn find_state(ctx: UIContext, id: int): option.Option[int]`

Index of the entry for id, or None if this context has never stored one. C16: this returned -1. Both callers happened to test it, which is why the sentinel never produced a wrong answer -- but see ensure_state below for what the SECOND -1 in this pair did cost.

`fn ensure_state(ctx: UIContext, id: int): option.Option[int]`

Index of the entry for id, creating one if the table has room, or None if the table is FULL.

ROADMAP 8.3 called the old return -1 here a silent drop, and the reason is one step further out than the sentinel: both callers DID test it, and then returned the unchanged UIContext anyway. Since a UIContext is a reference, that return value carried no information at all -- so a caller who filled the table got back the same context it passed in, with the value silently not stored and no way to tell. ui_set_float / ui_set_bool return bool now.

`fn ui_get_float(ctx: UIContext, id: int): option.Option[float]`

The Option form is the SOURCE OF TRUTH, and the _or twin delegates to it. It was the other way round: only the defaulted form existed, so a caller could not distinguish "stored 0.0" from "never stored", which is what 035_ERROR_HANDLING.md:427 requires the Option form to answer.

`fn ui_get_float_or(ctx: UIContext, id: int, default: float): float`

`fn ui_set_float(ctx: UIContext, id: int, value: float): bool`

True if the value was stored. False means this context's state table is full (MAX_STATE_VALUES entries) and the value was NOT kept -- which used to be indistinguishable from success, because this returned the same UIContext either way and a UIContext is a reference.

`fn ui_get_bool(ctx: UIContext, id: int): option.Option[bool]`

`fn ui_get_bool_or(ctx: UIContext, id: int, default: bool): bool`

`fn ui_set_bool(ctx: UIContext, id: int, value: bool): bool`

True if the value was stored. See ui_set_float.

`fn reef_int_to_float(i: int): float`

`fn int_to_float_ctx(i: int): float`

Procedures

`proc ui_begin_frame(ctx: UIContext)`

`proc ui_end_frame(ctx: UIContext)`

`proc update_line_height(ctx: UIContext, height: float)`

`proc advance_after_widget(ctx: UIContext, width: float, height: float)`

Called after drawing a widget to advance cursor

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