renderer: add zoom with detached camera (#12548)

src/config/ConfigDescriptions.hpp

@@ -1658,6 +1658,12 @@ inline static const std::vector<SConfigOptionDescription> CONFIG_OPTIONS = {
         .type        = CONFIG_OPTION_BOOL,
         .data        = SConfigOptionDescription::SBoolData{false},
     },
+    SConfigOptionDescription{
+        .value       = "cursor:zoom_detached_camera",
+        .description = "Detaches the camera from the mouse when zoomed in, only ever moving to keep the mouse in view",
+        .type        = CONFIG_OPTION_BOOL,
+        .data        = SConfigOptionDescription::SBoolData{true},
+    },
     SConfigOptionDescription{
         .value       = "cursor:enable_hyprcursor",
         .description = "whether to enable hyprcursor support",

src/config/ConfigManager.cpp

@@ -734,6 +734,7 @@ CConfigManager::CConfigManager() {
     registerConfigVar("cursor:zoom_factor", {1.f});
     registerConfigVar("cursor:zoom_rigid", Hyprlang::INT{0});
     registerConfigVar("cursor:zoom_disable_aa", Hyprlang::INT{0});
+    registerConfigVar("cursor:zoom_detached_camera", Hyprlang::INT{1});
     registerConfigVar("cursor:enable_hyprcursor", Hyprlang::INT{1});
     registerConfigVar("cursor:sync_gsettings_theme", Hyprlang::INT{1});
     registerConfigVar("cursor:hide_on_key_press", Hyprlang::INT{0});

src/helpers/Monitor.hpp

@@ -11,6 +11,7 @@
 #include "CMType.hpp"
 
 #include <xf86drmMode.h>
+#include "MonitorZoomController.hpp"
 #include "time/Timer.hpp"
 #include "math/Math.hpp"
 #include "../desktop/reserved/ReservedArea.hpp"
@@ -130,6 +131,8 @@ class CMonitor {
     uint32_t                    m_drmFormat     = DRM_FORMAT_INVALID;
     uint32_t                    m_prevDrmFormat = DRM_FORMAT_INVALID;
 
+    CMonitorZoomController      m_zoomController;
+
     bool                        m_dpmsStatus       = true;
     bool                        m_vrrActive        = false; // this can be TRUE even if VRR is not active in the case that this display does not support it.
     bool                        m_enabled10bit     = false; // as above, this can be TRUE even if 10 bit failed.

src/helpers/MonitorZoomController.cpp

@@ -0,0 +1,97 @@
+#include "MonitorZoomController.hpp"
+
+#include <hyprlang.hpp>
+#include "../config/ConfigValue.hpp"
+#include "../managers/input/InputManager.hpp"
+#include "../render/OpenGL.hpp"
+#include "desktop/DesktopTypes.hpp"
+#include "render/Renderer.hpp"
+
+void CMonitorZoomController::zoomWithDetachedCamera(CBox& result, const SCurrentRenderData& m_renderData) {
+    const auto m      = m_renderData.pMonitor;
+    auto       monbox = CBox(0, 0, m->m_size.x, m->m_size.y);
+    const auto ZOOM   = m_renderData.mouseZoomFactor;
+    const auto MOUSE  = g_pInputManager->getMouseCoordsInternal() - m->m_position;
+
+    if (m_lastZoomLevel != ZOOM) {
+        if (m_resetCameraState) {
+            m_resetCameraState = false;
+            m_camera           = CBox(0, 0, m->m_size.x, m->m_size.y);
+            m_lastZoomLevel    = 1.0f;
+        }
+        const CBox old = m_camera;
+
+        // mouse normalized inside screen (0..1)
+        const float mx = MOUSE.x / m->m_size.x;
+        const float my = MOUSE.y / m->m_size.y;
+        // world-space point under the cursor before zoom
+        const float mouseWorldX = old.x + (mx * old.w);
+        const float mouseWorldY = old.y + (my * old.h);
+
+        const auto  CAMERAW = monbox.w / ZOOM;
+        const auto  CAMERAH = monbox.h / ZOOM;
+
+        // compute new top-left so the same world point stays under the cursor
+        const float newX = mouseWorldX - (mx * CAMERAW);
+        const float newY = mouseWorldY - (my * CAMERAH);
+
+        m_camera = CBox(newX, newY, CAMERAW, CAMERAH);
+        // Detect if this zoom would've caused jerk to keep mouse in view and disable edges if so
+        if (!m_camera.copy().scaleFromCenter(.9).containsPoint(MOUSE))
+            m_padCamEdges = false;
+        m_lastZoomLevel = ZOOM;
+    }
+
+    // Keep mouse inside cameraview
+    auto smallerbox = m_camera;
+    // Prevent zoom step from causing us to jerk to keep mouse in padded camera view,
+    // but let us switch to the padded camera once the mouse moves into the safe area
+    if (!m_padCamEdges)
+        if (smallerbox.copy().scaleFromCenter(.9).containsPoint(MOUSE))
+            m_padCamEdges = true;
+    if (m_padCamEdges)
+        smallerbox.scaleFromCenter(.9);
+    if (!smallerbox.containsPoint(MOUSE)) {
+        if (MOUSE.x < smallerbox.x)
+            m_camera.x -= smallerbox.x - MOUSE.x;
+        if (MOUSE.y < smallerbox.y)
+            m_camera.y -= smallerbox.y - MOUSE.y;
+        if (MOUSE.y > smallerbox.y + smallerbox.h)
+            m_camera.y += MOUSE.y - (smallerbox.y + smallerbox.h);
+        if (MOUSE.x > smallerbox.x + smallerbox.w)
+            m_camera.x += MOUSE.x - (smallerbox.x + smallerbox.w);
+    }
+
+    auto z = ZOOM * m->m_scale;
+    monbox.scale(z).translate(-m_camera.pos() * z);
+
+    result = monbox;
+}
+
+void CMonitorZoomController::applyZoomTransform(CBox& monbox, const SCurrentRenderData& m_renderData) {
+    static auto PZOOMRIGID          = CConfigValue<Hyprlang::INT>("cursor:zoom_rigid");
+    static auto PZOOMDETACHEDCAMERA = CConfigValue<Hyprlang::INT>("cursor:zoom_detached_camera");
+    const auto  ZOOM                = m_renderData.mouseZoomFactor;
+
+    if (ZOOM == 1.0f)
+        return;
+
+    const auto m        = m_renderData.pMonitor;
+    const auto ORIGINAL = monbox;
+    const auto INITANIM = m->m_zoomAnimProgress->value() != 1.0;
+
+    if (*PZOOMDETACHEDCAMERA && !INITANIM)
+        zoomWithDetachedCamera(monbox, m_renderData);
+    else {
+        const auto ZOOMCENTER = m_renderData.mouseZoomUseMouse ? (g_pInputManager->getMouseCoordsInternal() - m->m_position) * m->m_scale : m->m_transformedSize / 2.f;
+
+        monbox.translate(-ZOOMCENTER).scale(ZOOM).translate(*PZOOMRIGID ? m->m_transformedSize / 2.0 : ZOOMCENTER);
+    }
+
+    monbox.x = std::min(monbox.x, 0.0);
+    monbox.y = std::min(monbox.y, 0.0);
+    if (monbox.x + monbox.width < ORIGINAL.w)
+        monbox.x = ORIGINAL.w - monbox.width;
+    if (monbox.y + monbox.height < ORIGINAL.h)
+        monbox.y = ORIGINAL.h - monbox.height;
+}

src/helpers/MonitorZoomController.hpp

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "./math/Math.hpp"
+
+struct SCurrentRenderData;
+
+class CMonitorZoomController {
+  public:
+    bool m_resetCameraState = true;
+
+    void applyZoomTransform(CBox& monbox, const SCurrentRenderData& m_renderData);
+
+  private:
+    void  zoomWithDetachedCamera(CBox& result, const SCurrentRenderData& m_renderData);
+
+    CBox  m_camera;
+    float m_lastZoomLevel = 1.0f;
+    bool  m_padCamEdges   = true;
+};

src/render/OpenGL.cpp

@@ -849,7 +849,6 @@ void CHyprOpenGLImpl::begin(PHLMONITOR pMonitor, const CRegion& damage_, CFrameb
 }
 
 void CHyprOpenGLImpl::end() {
-    static auto PZOOMRIGID     = CConfigValue<Hyprlang::INT>("cursor:zoom_rigid");
     static auto PZOOMDISABLEAA = CConfigValue<Hyprlang::INT>("cursor:zoom_disable_aa");
 
     TRACY_GPU_ZONE("RenderEnd");
@@ -861,20 +860,9 @@ void CHyprOpenGLImpl::end() {
 
         CBox monbox = {0, 0, m_renderData.pMonitor->m_transformedSize.x, m_renderData.pMonitor->m_transformedSize.y};
 
-        if (m_renderData.mouseZoomFactor != 1.f) {
-            const auto ZOOMCENTER = m_renderData.mouseZoomUseMouse ?
-                (g_pInputManager->getMouseCoordsInternal() - m_renderData.pMonitor->m_position) * m_renderData.pMonitor->m_scale :
-                m_renderData.pMonitor->m_transformedSize / 2.f;
-
-            monbox.translate(-ZOOMCENTER).scale(m_renderData.mouseZoomFactor).translate(*PZOOMRIGID ? m_renderData.pMonitor->m_transformedSize / 2.0 : ZOOMCENTER);
-
-            monbox.x = std::min(monbox.x, 0.0);
-            monbox.y = std::min(monbox.y, 0.0);
-            if (monbox.x + monbox.width < m_renderData.pMonitor->m_transformedSize.x)
-                monbox.x = m_renderData.pMonitor->m_transformedSize.x - monbox.width;
-            if (monbox.y + monbox.height < m_renderData.pMonitor->m_transformedSize.y)
-                monbox.y = m_renderData.pMonitor->m_transformedSize.y - monbox.height;
-        }
+        if (g_pHyprRenderer->m_renderMode == RENDER_MODE_NORMAL && m_renderData.mouseZoomFactor == 1.0f)
+            m_renderData.pMonitor->m_zoomController.m_resetCameraState = true;
+        m_renderData.pMonitor->m_zoomController.applyZoomTransform(monbox, m_renderData);
 
         m_applyFinalShader = !m_renderData.blockScreenShader;
         if (m_renderData.mouseZoomUseMouse && *PZOOMDISABLEAA)