From f0210e07972995550c2e4b71267e5f82eec0d6dd Mon Sep 17 00:00:00 2001
From: Kevin Reid <kpreid@switchb.org>
Date: Wed, 24 Jul 2024 14:43:30 -0700
Subject: [PATCH] ui: Move view transform calculation into `PageLayout`.

This makes sense to have in this module next to `UiSize`,
and will eventually actually depend on the layout.
---
 all-is-cubes-ui/src/ui_content/vui_manager.rs | 40 ++++++-------------
 all-is-cubes-ui/src/vui/page.rs               | 31 +++++++++++++-
 2 files changed, 42 insertions(+), 29 deletions(-)

diff --git a/all-is-cubes-ui/src/ui_content/vui_manager.rs b/all-is-cubes-ui/src/ui_content/vui_manager.rs
index 779b9ea5d..48b51b48f 100644
--- a/all-is-cubes-ui/src/ui_content/vui_manager.rs
+++ b/all-is-cubes-ui/src/ui_content/vui_manager.rs
@@ -7,8 +7,7 @@ use all_is_cubes::arcstr::ArcStr;
 use all_is_cubes::character::{Character, Cursor};
 use all_is_cubes::inv::{EphemeralOpaque, Tool, ToolError, ToolInput};
 use all_is_cubes::listen::{DirtyFlag, ListenableCell, ListenableSource, Notifier};
-use all_is_cubes::math::FreeCoordinate;
-use all_is_cubes::math::{FreeVector, NotNan};
+use all_is_cubes::math::NotNan;
 use all_is_cubes::space::Space;
 use all_is_cubes::time;
 use all_is_cubes::transaction::{self, Transaction};
@@ -237,10 +236,14 @@ impl Vui {
             } => &mut self.dump_page,
         };
         let next_space: Handle<Space> = next_page.get_or_create_space(size, universe);
+        let layout = next_page.page().layout;
 
         if Some(&next_space) != Option::as_ref(&self.current_view.get().space) {
-            self.current_view
-                .set(Self::view_state_for(Some(next_space), &self.hud_inputs));
+            self.current_view.set(Self::view_state_for(
+                layout,
+                Some(next_space),
+                &self.hud_inputs,
+            ));
             self.current_focus_on_ui = next_page.page().focus_on_ui;
             log::trace!(
                 "UI switched to {:?} ({:?})",
@@ -250,13 +253,17 @@ impl Vui {
         }
     }
 
-    fn view_state_for(space: Option<Handle<Space>>, inputs: &HudInputs) -> UiViewState {
+    fn view_state_for(
+        page_layout: vui::PageLayout,
+        space: Option<Handle<Space>>,
+        inputs: &HudInputs,
+    ) -> UiViewState {
         // TODO: compute the derived graphics options only once
         let graphics_options = Self::graphics_options(inputs.graphics_options.snapshot());
 
         UiViewState {
             view_transform: match space.as_ref() {
-                Some(space) => Self::view_transform(
+                Some(space) => page_layout.view_transform(
                     &space.read().unwrap(), // TODO: eliminate this unwrap
                     graphics_options.fov_y.into_inner(),
                 ),
@@ -267,27 +274,6 @@ impl Vui {
         }
     }
 
-    /// Computes a [`ViewTransform`] that should be used to view the [`Vui::current_space`].
-    ///
-    /// It does not need to be rechecked other than on aspect ratio changes.
-    ///
-    /// TODO: used to be public before [`UiViewState`]; refactor in light of
-    fn view_transform(space: &Space, fov_y_degrees: FreeCoordinate) -> ViewTransform {
-        let bounds = space.bounds();
-        let mut ui_center = bounds.center();
-
-        // Arrange a view distance which will place the Z=0 plane sized to fill the viewport
-        // (at least vertically, as we don't have aspect ratio support yet).
-        ui_center.z = 0.0;
-
-        let view_distance = FreeCoordinate::from(bounds.size().height)
-            / (fov_y_degrees / 2.).to_radians().tan()
-            / 2.;
-        ViewTransform::from_translation(
-            ui_center.to_vector() + FreeVector::new(0., 0., view_distance),
-        )
-    }
-
     /// Compute graphics options to render the VUI space given the user's regular options.
     fn graphics_options(mut options: GraphicsOptions) -> GraphicsOptions {
         // Set FOV to give a predictable, not-too-wide-angle perspective.
diff --git a/all-is-cubes-ui/src/vui/page.rs b/all-is-cubes-ui/src/vui/page.rs
index 6bcd2a144..190688905 100644
--- a/all-is-cubes-ui/src/vui/page.rs
+++ b/all-is-cubes-ui/src/vui/page.rs
@@ -7,12 +7,12 @@ use all_is_cubes::color_block;
 use all_is_cubes::content::palette;
 use all_is_cubes::euclid::{size2, Size2D};
 use all_is_cubes::math::{
-    Cube, Face6, FreeCoordinate, GridAab, GridCoordinate, GridSize, GridSizeCoord, Rgba,
+    Cube, Face6, FreeCoordinate, FreeVector, GridAab, GridCoordinate, GridSize, GridSizeCoord, Rgba,
 };
 use all_is_cubes::space::{self, Space, SpaceBuilder, SpacePhysics};
 use all_is_cubes::time;
 use all_is_cubes::universe::{Handle, Universe};
-use all_is_cubes_render::camera;
+use all_is_cubes_render::camera::{self, ViewTransform};
 
 use crate::vui::{
     self, install_widgets, widgets, Align, Gravity, InstallVuiError, LayoutGrant, LayoutRequest,
@@ -160,6 +160,33 @@ pub(crate) enum PageLayout {
     Hud,
 }
 
+impl PageLayout {
+    /// Calculate the camera view transform that should be used for a page with this layout.
+    pub(crate) fn view_transform(
+        self,
+        space: &Space,
+        fov_y_degrees: FreeCoordinate,
+    ) -> ViewTransform {
+        let bounds = space.bounds();
+        let mut ui_center = bounds.center();
+
+        match self {
+            PageLayout::Hud => {
+                // Arrange a view distance which will place the Z=0 plane sized to fill the viewport
+                // vertically.
+                ui_center.z = 0.0;
+
+                let view_distance = FreeCoordinate::from(bounds.size().height)
+                    / (fov_y_degrees / 2.).to_radians().tan()
+                    / 2.;
+                ViewTransform::from_translation(
+                    ui_center.to_vector() + FreeVector::new(0., 0., view_distance),
+                )
+            }
+        }
+    }
+}
+
 /// Pair of a [`Page`] and a cached space that is an instantiation of its widgets,
 /// which can be recreated with a different size as needed by viewport size changes.
 ///