From c963c60a0fe5319fe97d9733fda171020bcf5441 Mon Sep 17 00:00:00 2001
From: Artur Wieczorek <artwik@wp.pl>
Date: Mon, 18 May 2020 18:52:41 +0200
Subject: [PATCH] Determine initial wxSpinCtrlDouble precision

For native wxGTK implementation default spin control precision is derived
from the precision of the increment value. Fot the sake of consistency the
same should be done in the generic implementation.

Closes #18764.
---
 include/wx/generic/spinctlg.h |  2 ++
 src/generic/spinctlg.cpp      | 14 +++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/wx/generic/spinctlg.h b/include/wx/generic/spinctlg.h
index c3d2e9eef5..ff3c8ca2ed 100644
--- a/include/wx/generic/spinctlg.h
+++ b/include/wx/generic/spinctlg.h
@@ -380,6 +380,7 @@ public:
                 double inc = 1,
                 const wxString& name = wxT("wxSpinCtrlDouble"))
     {
+        DetermineDigits(inc);
         return wxSpinCtrlGenericBase::Create(parent, id, value, pos, size,
                                              style, min, max, initial,
                                              inc, name);
@@ -410,6 +411,7 @@ protected:
 
     virtual bool DoTextToValue(const wxString& text, double *val) wxOVERRIDE;
     virtual wxString DoValueToText(double val) wxOVERRIDE;
+    void DetermineDigits(double inc);
 
     unsigned m_digits;
 
diff --git a/src/generic/spinctlg.cpp b/src/generic/spinctlg.cpp
index 0620948741..29443b6f3d 100644
--- a/src/generic/spinctlg.cpp
+++ b/src/generic/spinctlg.cpp
@@ -673,6 +673,8 @@ wxString wxSpinCtrl::DoValueToText(double val)
 // wxSpinCtrlDouble
 //-----------------------------------------------------------------------------
 
+#define SPINCTRLDBL_MAX_DIGITS 20
+
 wxIMPLEMENT_DYNAMIC_CLASS(wxSpinCtrlDouble, wxSpinCtrlGenericBase);
 
 void wxSpinCtrlDouble::DoSendEvent()
@@ -696,7 +698,7 @@ wxString wxSpinCtrlDouble::DoValueToText(double val)
 
 void wxSpinCtrlDouble::SetDigits(unsigned digits)
 {
-    wxCHECK_RET( digits <= 20, "too many digits for wxSpinCtrlDouble" );
+    wxCHECK_RET( digits <= SPINCTRLDBL_MAX_DIGITS, "too many digits for wxSpinCtrlDouble" );
 
     if ( digits == m_digits )
         return;
@@ -708,6 +710,16 @@ void wxSpinCtrlDouble::SetDigits(unsigned digits)
     DoSetValue(m_value, SendEvent_None);
 }
 
+void wxSpinCtrlDouble::DetermineDigits(double inc)
+{
+    inc = fabs(inc);
+    if ( inc > 0.0 && inc < 1.0 )
+    {
+        m_digits = wxMin(SPINCTRLDBL_MAX_DIGITS, -static_cast<int>(floor(log10(inc))));
+        m_format.Printf("%%0.%ulf", m_digits);
+    }
+}
+
 #endif // wxUSE_SPINBTN
 
 #endif // !wxPort-with-native-spinctrl