From 374571da96ea65f810387c5ff1872d3950076d08 Mon Sep 17 00:00:00 2001
From: vaxerski <43317083+vaxerski@users.noreply.github.com>
Date: Wed, 14 Dec 2022 17:57:18 +0000
Subject: [PATCH] add auto scale

---
 src/config/ConfigManager.cpp | 12 ++++++++----
 src/helpers/Monitor.cpp      | 18 ++++++++++++++++++
 src/helpers/Monitor.hpp      |  1 +
 src/render/Renderer.cpp      | 10 ++++++++--
 4 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/src/config/ConfigManager.cpp b/src/config/ConfigManager.cpp
index 1092b1c4..345ba3af 100644
--- a/src/config/ConfigManager.cpp
+++ b/src/config/ConfigManager.cpp
@@ -504,11 +504,15 @@ void CConfigManager::handleMonitor(const std::string& command, const std::string
         }
     }
 
-    newrule.scale = stof(ARGS[3]);
+    if (ARGS[3].find("auto") == 0) {
+        newrule.scale = -1;
+    } else {
+        newrule.scale = stof(ARGS[3]);
 
-    if (newrule.scale < 0.25f) {
-        parseError = "not a valid scale.";
-        newrule.scale = 1;
+        if (newrule.scale < 0.25f) {
+            parseError = "not a valid scale.";
+            newrule.scale = 1;
+        }
     }
 
     int argno = 4;
diff --git a/src/helpers/Monitor.cpp b/src/helpers/Monitor.cpp
index d7daa355..d322cee5 100644
--- a/src/helpers/Monitor.cpp
+++ b/src/helpers/Monitor.cpp
@@ -394,3 +394,21 @@ void CMonitor::setMirror(const std::string& mirrorOf) {
         g_pCompositor->setActiveMonitor(g_pCompositor->m_vMonitors.front().get());
     }
 }
+
+float CMonitor::getDefaultScale() {
+    if (!m_bEnabled)
+        return 1;
+
+    static constexpr double MMPERINCH = 25.4;
+
+    const auto DIAGONALPX = sqrt(pow(vecPixelSize.x, 2) + pow(vecPixelSize.y, 2));
+    const auto DIAGONALIN = sqrt(pow(output->phys_width / MMPERINCH, 2) + pow(output->phys_height / MMPERINCH, 2));
+
+    const auto PPI = DIAGONALPX / DIAGONALIN;
+
+    if (PPI > 200 /* High PPI, 2x*/)
+        return 2;
+    else if (PPI > 125 /* Medium PPI, 1.5x*/)
+        return 1.5;
+    return 1;
+}
diff --git a/src/helpers/Monitor.hpp b/src/helpers/Monitor.hpp
index 4164b223..b5fea7a9 100644
--- a/src/helpers/Monitor.hpp
+++ b/src/helpers/Monitor.hpp
@@ -70,6 +70,7 @@ public:
     void        addDamage(wlr_box* box);
     void        setMirror(const std::string&);
     bool        isMirror();
+    float       getDefaultScale();
 
     std::shared_ptr<CMonitor>* m_pThisWrap = nullptr;
     bool        m_bEnabled = false;
diff --git a/src/render/Renderer.cpp b/src/render/Renderer.cpp
index 9c8354ec..20e77afe 100644
--- a/src/render/Renderer.cpp
+++ b/src/render/Renderer.cpp
@@ -1141,8 +1141,14 @@ bool CHyprRenderer::applyMonitorRule(CMonitor* pMonitor, SMonitorRule* pMonitorR
         return true;
     }
 
-    wlr_output_set_scale(pMonitor->output, pMonitorRule->scale);
-    pMonitor->scale = pMonitorRule->scale;
+    if (pMonitorRule->scale != -1) {
+        wlr_output_set_scale(pMonitor->output, pMonitorRule->scale);
+        pMonitor->scale = pMonitorRule->scale;
+    } else {
+        const auto DEFAULTSCALE = pMonitor->getDefaultScale();
+        wlr_output_set_scale(pMonitor->output, DEFAULTSCALE);
+        pMonitor->scale = DEFAULTSCALE;
+    }
 
     wlr_output_set_transform(pMonitor->output, pMonitorRule->transform);
     pMonitor->transform = pMonitorRule->transform;