panopainter/src/app_core/app_frame.h

#pragma once

#include "foundation/result.h"

#include <cmath>
#include <cstdint>
#include <limits>
#include <span>

namespace pp::app {

struct AppInitialSurfacePlan {
    float width = 960.0F;
    float height = 540.0F;
};

struct AppFrameUpdatePlan {
    bool update_frame = false;
    bool update_layouts = false;
    bool refresh_canvas_toolbar = false;
};

struct AppFrameDrawPlan {
    bool draw_canvas_stroke = false;
    bool draw_vr_ui = false;
    bool draw_main_ui = true;
    bool reset_redraw = true;
};

struct AppFrameTickPlan {
    bool tick_designer_layout = false;
    bool tick_main_layout = false;
};

struct AppResizePlan {
    float width = 0.0F;
    float height = 0.0F;
    int render_target_width = 0;
    int render_target_height = 0;
    bool recreate_ui_render_target = true;
    bool request_redraw = true;
};

struct AppUiObserverRect {
    float x = 0.0F;
    float y = 0.0F;
    float width = 0.0F;
    float height = 0.0F;
};

struct AppUiObserverParentClip {
    AppUiObserverRect clip;
    float padding_top = 0.0F;
    float padding_right = 0.0F;
    float padding_bottom = 0.0F;
    float padding_left = 0.0F;
};

struct AppUiObserverPlan {
    bool draw_node = false;
    bool notify_enter_screen = false;
    bool notify_leave_screen = false;
    bool next_on_screen = false;
    AppUiObserverRect visible_clip;
    std::int32_t scissor_x = 0;
    std::int32_t scissor_y = 0;
    std::int32_t scissor_width = 0;
    std::int32_t scissor_height = 0;
};

[[nodiscard]] constexpr AppInitialSurfacePlan plan_app_initial_surface() noexcept
{
    return AppInitialSurfacePlan {
        .width = 1920.0F / 2.0F,
        .height = 1080.0F / 2.0F,
    };
}

[[nodiscard]] constexpr AppFrameUpdatePlan plan_app_frame_update(bool redraw, bool animate) noexcept
{
    const bool update_frame = redraw || animate;
    return AppFrameUpdatePlan {
        .update_frame = update_frame,
        .update_layouts = update_frame,
        .refresh_canvas_toolbar = update_frame,
    };
}

[[nodiscard]] constexpr AppFrameDrawPlan plan_app_frame_draw(
    bool has_canvas_node,
    bool has_canvas_document,
    bool vr_active,
    bool ui_visible,
    bool vr_only) noexcept
{
    return AppFrameDrawPlan {
        .draw_canvas_stroke = has_canvas_node && has_canvas_document,
        .draw_vr_ui = vr_active && ui_visible,
        .draw_main_ui = !vr_only,
        .reset_redraw = true,
    };
}

[[nodiscard]] constexpr AppFrameTickPlan plan_app_frame_tick(
    bool has_designer_layout,
    bool has_main_layout) noexcept
{
    return AppFrameTickPlan {
        .tick_designer_layout = has_designer_layout,
        .tick_main_layout = has_main_layout,
    };
}

[[nodiscard]] inline pp::foundation::Result<AppResizePlan> plan_app_resize(float width, float height)
{
    if (!std::isfinite(width) || !std::isfinite(height)) {
        return pp::foundation::Result<AppResizePlan>::failure(
            pp::foundation::Status::invalid_argument("resize dimensions must be finite"));
    }

    if (width < 1.0F || height < 1.0F) {
        return pp::foundation::Result<AppResizePlan>::failure(
            pp::foundation::Status::invalid_argument("resize dimensions must be positive"));
    }

    if (width > static_cast<float>(std::numeric_limits<int>::max())
        || height > static_cast<float>(std::numeric_limits<int>::max())) {
        return pp::foundation::Result<AppResizePlan>::failure(
            pp::foundation::Status::out_of_range("resize dimensions exceed integer range"));
    }

    return pp::foundation::Result<AppResizePlan>::success(AppResizePlan {
        .width = width,
        .height = height,
        .render_target_width = static_cast<int>(width),
        .render_target_height = static_cast<int>(height),
        .recreate_ui_render_target = true,
        .request_redraw = true,
    });
}

[[nodiscard]] constexpr AppUiObserverRect intersect_app_ui_observer_rect(
    AppUiObserverRect a,
    AppUiObserverRect b) noexcept
{
    const float x0 = a.x > b.x ? a.x : b.x;
    const float y0 = a.y > b.y ? a.y : b.y;
    const float x1 = (a.x + a.width) < (b.x + b.width) ? (a.x + a.width) : (b.x + b.width);
    const float y1 = (a.y + a.height) < (b.y + b.height) ? (a.y + a.height) : (b.y + b.height);
    return AppUiObserverRect {
        .x = x0,
        .y = y0,
        .width = x1 - x0,
        .height = y1 - y0,
    };
}

[[nodiscard]] inline pp::foundation::Result<AppUiObserverPlan> plan_app_ui_observer(
    bool has_node,
    bool display,
    bool was_on_screen,
    AppUiObserverRect node_clip,
    std::span<const AppUiObserverParentClip> parent_clips,
    float surface_height,
    float zoom,
    float offset_x,
    float offset_y)
{
    if (!has_node || !display) {
        return pp::foundation::Result<AppUiObserverPlan>::success(AppUiObserverPlan {
            .draw_node = false,
            .next_on_screen = was_on_screen,
            .visible_clip = node_clip,
        });
    }

    const auto finite_rect = [](AppUiObserverRect rect) noexcept {
        return std::isfinite(rect.x) && std::isfinite(rect.y)
            && std::isfinite(rect.width) && std::isfinite(rect.height);
    };

    if (!finite_rect(node_clip) || !std::isfinite(surface_height)
        || !std::isfinite(zoom) || !std::isfinite(offset_x) || !std::isfinite(offset_y)) {
        return pp::foundation::Result<AppUiObserverPlan>::failure(
            pp::foundation::Status::invalid_argument("UI observer geometry must be finite"));
    }

    if (surface_height < 1.0F || zoom <= 0.0F) {
        return pp::foundation::Result<AppUiObserverPlan>::failure(
            pp::foundation::Status::invalid_argument("UI observer surface height and zoom must be positive"));
    }

    AppUiObserverRect visible = node_clip;
    for (const auto& parent : parent_clips) {
        if (!finite_rect(parent.clip)
            || !std::isfinite(parent.padding_top)
            || !std::isfinite(parent.padding_right)
            || !std::isfinite(parent.padding_bottom)
            || !std::isfinite(parent.padding_left)) {
            return pp::foundation::Result<AppUiObserverPlan>::failure(
                pp::foundation::Status::invalid_argument("UI observer parent geometry must be finite"));
        }

        const AppUiObserverRect padded {
            .x = parent.clip.x + parent.padding_left,
            .y = parent.clip.y + parent.padding_top,
            .width = parent.clip.width - parent.padding_right - parent.padding_left,
            .height = parent.clip.height - parent.padding_bottom - parent.padding_top,
        };
        visible = intersect_app_ui_observer_rect(visible, padded);
    }

    if (visible.width <= 0.0F || visible.height <= 0.0F) {
        return pp::foundation::Result<AppUiObserverPlan>::success(AppUiObserverPlan {
            .draw_node = false,
            .notify_leave_screen = was_on_screen,
            .next_on_screen = false,
            .visible_clip = visible,
        });
    }

    const float projected_x = (visible.x - 1.0F) * zoom;
    const float projected_y = (surface_height / zoom - visible.y - visible.height - 1.0F) * zoom;
    const float projected_width = (visible.width + 2.0F) * zoom;
    const float projected_height = (visible.height + 2.0F) * zoom;

    return pp::foundation::Result<AppUiObserverPlan>::success(AppUiObserverPlan {
        .draw_node = true,
        .notify_enter_screen = !was_on_screen,
        .notify_leave_screen = false,
        .next_on_screen = true,
        .visible_clip = visible,
        .scissor_x = static_cast<std::int32_t>(std::floor(projected_x + offset_x)),
        .scissor_y = static_cast<std::int32_t>(std::floor(projected_y + offset_y)),
        .scissor_width = static_cast<std::int32_t>(std::ceil(projected_width)),
        .scissor_height = static_cast<std::int32_t>(std::ceil(projected_height)),
    });
}

} // namespace pp::app