From d3c4d4dfb28a518bff924764e74ca4ededf1bd41 Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Thu, 12 Mar 2026 15:30:15 -0700
Subject: Support for scrolling by dragging scrollbars

---
 src/xplorer.c | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/xplorer.c b/src/xplorer.c
index c03a16e..6dd1bbf 100644
--- a/src/xplorer.c
+++ b/src/xplorer.c
@@ -10,6 +10,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+// TODO: Set window dimensions and font size based on pixel area density.
 static const char* WindowTitle   = "XPLORER";
 static const int   DefaultWidth  = 720;
 static const int   DefaultHeight = 450;
@@ -34,6 +35,9 @@ uiMouseButton ToUiButton(Uint8 button);
 void MouseCoordsToUiCoords(
     SDL_Window*, float mouse_x, float mouse_y, int* x, int* y);
 
+uiMouseButtonState MouseButtonStateFromFlags(
+    SDL_MouseButtonFlags flags, uiMouseButton button);
+
 void CreateUi(State* state) {
   assert(state);
 
@@ -345,7 +349,7 @@ int main(
           .type = uiEventMouseButton,
           .mouse_button =
               (uiMouseButtonEvent){.button = ToUiButton(event.button.button),
-                                   .state  = uiMouseDown,
+                                   .button_state   = uiMouseDown,
                                    .mouse_position = (uiPoint){x, y}}
       };
       redraw = uiSendEvent(state.frame, &ui_event);
@@ -357,7 +361,7 @@ int main(
           .type = uiEventMouseButton,
           .mouse_button =
               (uiMouseButtonEvent){.button = ToUiButton(event.button.button),
-                                   .state  = uiMouseUp,
+                                   .button_state   = uiMouseUp,
                                    .mouse_position = (uiPoint){x, y}}
       };
       redraw = uiSendEvent(state.frame, &ev);
@@ -365,6 +369,11 @@ int main(
       int x, y;
       MouseCoordsToUiCoords(
           state.window, event.wheel.mouse_x, event.wheel.mouse_y, &x, &y);
+      // TODO: Scrolling on a trackpad results in 0<event.wheel.y<1 values,
+      //  which become 0 with integer truncation. Have the UI library handle
+      //  float values for smooth scrolling. Though that means a lot of the UI
+      //  input will have to be float-based. Should we handle it here in the
+      //  client instead? That seems inconvenient.
       const uiInputEvent ev = {
           .type = uiEventMouseScroll,
           .mouse_scroll =
@@ -372,6 +381,20 @@ int main(
                                    .mouse_position = (uiPoint){x, y}}
       };
       redraw = uiSendEvent(state.frame, &ev);
+    } else if (event.type == SDL_EVENT_MOUSE_MOTION) {
+      int x, y;
+      MouseCoordsToUiCoords(
+          state.window, event.motion.x, event.motion.y, &x, &y);
+      const uiInputEvent ev = {
+          .type       = uiEventMouseMove,
+          .mouse_move = (uiMouseMoveEvent){
+                                           .button_state =
+                  {
+                      MouseButtonStateFromFlags(event.motion.state, uiLMB),
+                      MouseButtonStateFromFlags(event.motion.state, uiRMB),
+                  }, .mouse_position = (uiPoint){x, y}}
+      };
+      redraw = uiSendEvent(state.frame, &ev);
     } else {
       EVENT_LOOP_PRINT("event.window.event = %d\n", event.window.event);
     }
@@ -417,3 +440,16 @@ void MouseCoordsToUiCoords(
   *x            = (int)(mouse_x * d);
   *y            = (int)(mouse_y * d);
 }
+
+uiMouseButtonState MouseButtonStateFromFlags(
+    SDL_MouseButtonFlags flags, uiMouseButton button) {
+  switch (button) {
+  case uiLMB:
+    return (flags & SDL_BUTTON_LMASK) ? uiMouseDown : uiMouseUp;
+  case uiRMB:
+    return (flags & SDL_BUTTON_RMASK) ? uiMouseDown : uiMouseUp;
+  default:
+    assert(false);
+    return uiMouseUp;
+  }
+}
-- 
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