[input] distinguish between clicks and drag

You can now drag a button in a scroll area to scroll

emigui/README.md

@@ -77,7 +77,7 @@ Add extremely quick animations for some things, maybe 2-3 frames. For instance:
     * e.g. `ui.containers((Frame::new(), Resize::new(), ScrollArea::new()), |ui| ...)`
 
 ### Input
-* [ ] Distinguish between clicks and drags
+* [x] Distinguish between clicks and drags
 * [ ] Double-click
 * [x] Text
 

emigui/src/containers/scroll_area.rs

@@ -154,7 +154,7 @@ impl Prepared {
         }
 
         // TODO: check that nothing else is being inteacted with
-        if ui.contains_mouse(outer_rect) && ui.memory().active_id.is_none() {
+        if ui.contains_mouse(outer_rect) {
             state.offset.y -= ui.input().scroll_delta.y;
         }
 

emigui/src/containers/window.rs

@@ -358,9 +358,9 @@ fn window_interaction(
     rect: Rect,
 ) -> Option<WindowInteraction> {
     {
-        let active_id = ctx.memory().active_id;
+        let drag_id = ctx.memory().interaction.drag_id;
 
-        if active_id.is_some() && active_id != Some(id) {
+        if drag_id.is_some() && drag_id != Some(id) {
             return None;
         }
     }
@@ -371,7 +371,7 @@ fn window_interaction(
         if let Some(hover_window_interaction) = resize_hover(ctx, possible, area_layer, rect) {
             hover_window_interaction.set_cursor(ctx);
             if ctx.input().mouse.pressed {
-                ctx.memory().active_id = Some(id);
+                ctx.memory().interaction.drag_id = Some(id);
                 window_interaction = Some(hover_window_interaction);
                 ctx.memory().window_interaction = window_interaction;
             }
@@ -379,7 +379,7 @@ fn window_interaction(
     }
 
     if let Some(window_interaction) = window_interaction {
-        let is_active = ctx.memory().active_id == Some(id);
+        let is_active = ctx.memory().interaction.drag_id == Some(id);
 
         if is_active && window_interaction.area_layer == area_layer {
             return Some(window_interaction);

emigui/src/context.rs

@@ -147,9 +147,14 @@ impl Context {
     }
 
     fn begin_frame_mut(&mut self, new_raw_input: RawInput) {
+        if !self.input().mouse.could_be_click {
+            self.memory().interaction.click_id = None;
+        }
+
         if !self.input.mouse.down || self.input.mouse.pos.is_none() {
             // mouse was not down last frame
-            self.memory().active_id = None;
+            self.memory().interaction.click_id = None;
+            self.memory().interaction.drag_id = None;
 
             let window_interaction = self.memory().window_interaction.take();
             if let Some(window_interaction) = window_interaction {
@@ -234,11 +239,6 @@ impl Context {
 
     // ---------------------------------------------------------------------
 
-    /// Is the user interacting with anything?
-    pub fn any_active(&self) -> bool {
-        self.memory().active_id.is_some()
-    }
-
     /// Generate a id from the given source.
     /// If it is not unique, an error will be printed at the given position.
     pub fn make_unique_id<IdSource>(&self, source: IdSource, pos: Pos2) -> Id
@@ -307,39 +307,31 @@ impl Context {
         let interaction_id = interaction_id.unwrap();
 
         let mut memory = self.memory();
-        let active = memory.active_id == Some(interaction_id);
+        let active = memory.interaction.click_id == Some(interaction_id)
-
+            || memory.interaction.drag_id == Some(interaction_id);
-        if active && !sense.drag && !self.input().mouse.could_be_click {
-            // Aborted click
-            memory.active_id = None;
-            return InteractInfo {
-                rect,
-                hovered: false,
-                clicked: false,
-                active: false,
-            };
-        }
 
         if self.input.mouse.pressed {
             if hovered {
-                if memory.active_id.is_some() {
+                let mut info = InteractInfo {
-                    // Already clicked something else this frame
-                    InteractInfo {
                     rect,
-                        hovered,
+                    hovered: true,
                     clicked: false,
                     active: false,
+                };
+
+                if sense.click && !memory.interaction.click_id.is_some() {
+                    // start of a click
+                    memory.interaction.click_id = Some(interaction_id);
+                    info.active = true;
                 }
-                } else {
+
-                    // start of a click or drag
+                if sense.drag && !memory.interaction.drag_id.is_some() {
-                    memory.active_id = Some(interaction_id);
+                    // start of a drag
-                    InteractInfo {
+                    memory.interaction.drag_id = Some(interaction_id);
-                        rect,
+                    info.active = true;
-                        hovered,
-                        clicked: false,
-                        active: true,
-                    }
                 }
+
+                info
             } else {
                 // miss
                 InteractInfo {

emigui/src/memory.rs

@@ -9,9 +9,8 @@ use crate::{
 #[derive(Clone, Debug, Default, serde_derive::Deserialize, serde_derive::Serialize)]
 #[serde(default)]
 pub struct Memory {
-    /// The widget being interacted with (e.g. dragged, in case of a slider).
     #[serde(skip)]
-    pub(crate) active_id: Option<Id>,
+    pub(crate) interaction: Interaction,
 
     /// The widget with keyboard focus (i.e. a text input field).
     #[serde(skip)]
@@ -30,6 +29,22 @@ pub struct Memory {
     pub(crate) areas: Areas,
 }
 
+/// Say there is a butotn in a scroll area.
+/// If the user clicks the button, the button should click.
+/// If the user drags the button we should scroll the scroll area.
+/// So what we do is that when the mouse is pressed we register both the button
+/// and the scroll area (as `click_id`/`drag_id`).
+/// If the user releases the button without moving the mouse we register it as a click on `click_id`.
+/// If the cursor moves too much we clear the `click_id` and start passing move events to `drag_id`.
+#[derive(Clone, Debug, Default)]
+pub struct Interaction {
+    /// A widget interested in clicks that has a mouse press on it.
+    pub click_id: Option<Id>,
+
+    /// A widget interested in drags that has a mouse press on it.
+    pub drag_id: Option<Id>,
+}
+
 #[derive(Clone, Debug, Default, serde_derive::Deserialize, serde_derive::Serialize)]
 #[serde(default)]
 pub struct Areas {